In the world of high-end luxury cars, Audi A8 stands alone, set apart from such stylish competition as Jaguar, Mercedes-Benz, Lexus or Cadillac.

What makes A8 unique is what A8 is made of: aluminum. From its body panels and five-valve V-8 engine to its underlying space frame, A8's aluminum construction gives the flagship Audi an undeniably exotic spin.

Aluminum also lightens the weight of this big craft, compared with steel, and enhances the sedan's supple ride and nimble handling. The A8, new for '97 after 10 years of development by Audi engineers teamed up with aluminum-expert Alcoa, sets the standard for alloy sedan construction.

For those who picture aluminum as exclusive to soda cans and foil for the barbecue, understand that A8 is a very substantial automobile. Weighing in at around 2 tons despite the lightweight material, A8 has the solid, vaultlike feel of the top competition, along with Audi's signature cornering prowess.

The downside of aluminum construction is that it's notoriously difficult and expensive to fix after a collision.

The test car was the A8 L long-wheelbase version, nearly 5 inches longer than the standard A8 (which is already plenty big), with the additional inches mainly benefiting rear-seat passengers. And that rear seat is huge, spacious enough for a German chancellor and a couple other heads of state, with their hats on.

Despite its formidable size, A8 is quick and maneuverable, with the lightness of the aluminum structure shining through. The space frame is touted by Audi for its stiffness, and the sedan does feel solid and stable.

That mighty V8, with its variable valve timing and intake runners, pulls like a turbine, smooth and strong from idle all the way up to its nearly 7,000 rpm redline. In cubic inches (remember them?), it's just a 255, tiny in V-8 terms. Yet it puts out a clean 310 horsepower with a minimum of fuss.

The steering is quick though quite light to the touch, for a German car.

Part of A8's superior handling comes from its standard Quattro all-wheel-drive system, which Audi pioneered more than two decades ago.

The suspension of the A8 is fairly soft, a real boulevard cruiser. The car feels mushy over some surfaces but surprisingly harsh over others.

New for 2001 is a hot-rod version of the short-wheelbase sedan called the S8, with 50 more horsepower plus steering and suspension more attuned to serious driving.

The A8's handling and crash avoidance is enhanced by several electronic marvels, including an advanced form of traction control, anti-lock brakes, automatic locking differential for low-traction start-ups and electronic stability control, which helps keep the car out of skids through an array of sensors and computing functions.

On the road, the A8 is eerily quiet, with just a distant howl from the engine under acceleration. Part of that quiet may be attributable to the sound-deadening qualities of aluminum.

In any case, the leather- and wood-lined cabin feels secure and removed from the traffic outside. All the better to listen to the excellent Bose stereo or fool around with the navigation system. Naturally, every power, safety and convenience accessory known to man is present, including a radar system that warns the driver of impending parking-maneuver collisions to the rear and sides.

All this and the price is just, well, it's expensive. Real expensive as in hovering around the $70,000 mark.

The total included $1,200 for "pearlescent white clearcoat," $1,500 for 18-inch wheels and performance tires, $500 for high-intensity headlights, $700 for the radar warning system and $200 for a ski sack.

As top-drawer cars go, the A8 L is a beauty, offering a different take on Germanic luxury than Mercedes-Benz S-Class or BMW 7-Series. Anyone shopping in this rarefied atmosphere should check ou the difference in style, performance and aluminum.