AMID the urban shimmer of Heat, the cop and the crook are flip sides of the same steel coin. That should be trite, but not when the actors doing the tossing are Al Pacino and Robert De Niro. Icons of identical intensity, albeit achieved through singularly different means, they've never worked together before (their scenes in The Godfather saga didn't intersect); so you anticipate the union with high excitement tempered by slight dread. Dream match-ups on paper don't always succeed on the screen - like twin fires fighting for oxygen, will they merely cancel each other out? Hardly. This is one titanic clash that actually lives up to the billing, and Heat rises on the pure flame of their talent.

No, the film may not be quite as luminous as the cast, but it's good - very good, in fact. Director Michael Mann has long had a flair for putting the motion in the picture, but he's now added the grace note of impeccable pacing - knowing just when to slow the action down. He's figured out something else too - how to showcase his bright stars, keeping them firmly in character while still taking advantage of their celebrated reputations. After all, it's not just the cop and the crook who are squaring off here - it's Serpico and Taxi Driver, it's Scarface and Raging Bull, it's Scarecrow and The Deer Hunter. Mann understands this ripple effect, and lets it play out as a delicious undercurrent beneath the fictional text.

He starts at a pulse-pounding speed, bathing Los Angeles in the same high-tech glow he brought to Miami Vice, only colder, and greeting us with a slickly edited montage that quotes the opening heist in Thief, only longer. Much, much longer - for virtually the entire first act, an extended ribbon of parallel scenes weaves between the criminal action and the police reaction. Together with his crew, Neil (De Niro) pulls off a daring robbery of an armoured truck; the man is a master - cerebral, cool, meticulous, lethally efficient. Of course, Pacino is the legal heat - his Vincent is the fire to Neil's ice, and when the breathless action finally takes a pause, their dual characterization can begin.

We soon discover that Neil and Vince are matching halves of a vicious equation - all that separates them is the narrow hyphen of the law, and the even smaller matter of style. Otherwise, each is essentially alone yet neither is lonely; work is their constant companion - it's what they do best, and they do it extraordinarily well. When folks ask about their dark days, they shrug and offer a word-for-word echo: "You don't want to know."

Sure, women beckon, but Vince's third marriage is already in trouble; his wife (a riveting turn by Diane Venora) is tired of his absences, while his step-daughter is a step away from despair - no one has time for her. Neil is less hypocritical; he lives isolated in a house by the beach, a sparse palace furnished with nothing more than a splendid view, the better to honour his credo: "Don't get attracted to anything you can't leave in 30 seconds, when you spot the heat around the corner." He falters once, stumbling into love with a sweet young thing (Amy Brenneman), yet not to worry - we're damned sure he won't trip.

Assuredly, the cop and the crook need each other - their antagonism is the only real bond in their lives - and, eventually, that need gets satisfied in a face-to-face meeting, a brief interlude over coffee that bisects the film like the stem in an hourglass (actually, 2-3/4 hourglass) . Let's call it THE SCENE, the icons' first shared frame, and it's a joy to watch, both as a pivotal confrontation in the story and as a straight mano a mano between the actors. So text and subtext neatly meld; here too, the styles are markedly different - Pacino's more flamboyant and bold; De Niro's more subdued and allusive - but the substance is equally sublime.

Who wins? Pick 'em.

From there, they split, and it's a lengthy chase to the finish. But I neglect the plot, a busy narrative that Mann stuffs with plenty of sidebars and near-cliches. Happily, he redeems them from tediousness, partly by sticking to his thematic guns in order to avoid cheap sentiment, and partly with the help of a terrific supporting cast. Val Kilmer is a presence unto himself as Neil's protege, a sharpshooter who admires his boss's guile yet can't abide his credo - he's attached at the hip to his wife ("For me, the sun rises and sets on her"), and his fate is an ironic joke at Neil's expense, a sly aside sneaked quietly into the folds of the script. Also, Jon Voigt submits a splendid cameo as a behind-the-scenes mentor - although his face bears the deep scars of past criminal wars (he looks like a midnight cowboy at 3 a.m.), the guy is a survivor, an old double-dealer now content to let the cards fall where they may.

Not Neil. He's obsessively thorough and thoroughly obsessed - it's his disdain for the loose end that ultimately leads to his own end, and a climax that seems mildly disappointing, more in tune with a standard Hollywood actioner than with anything that preceded it. Up until then, Mann, like so many others, had ripped a page from Quentin Tarrantino's book (the Reservoir Dogs chapter, not Pulp Fiction). However, unlike the others, he's wedded that borrowing to a distinctive visual sense (always a Mann trademark), and the blend is awfully satisfying - think of it as "bleak chic" squared. That may be a familiar sight these days, yet, with De Niro and Pacino factored in, resistance is useless. Such bursts of calculated speed, such blasts of performing artistry, it's no contest - Heat will melt your defences.