AFTER the sedan, Avant, A5 Coupe, A5 Cabrio and S5 variants, Audi is on the niche trail again with yet another A4 spinoff, the A5 Sportback. From a distance it looks like the regular Audi sedan, but close scrutiny reveals four seats, a swoopier profile, an A5 Coupe nose and a great big tailgate. Audi says there’s never been a car like this, and if you are inclined to buy a coupe but can’t handle having two doors and limited luggage capacity, this might just be your cup of tea.