Apparently Hartmann and Pokryshkin (Sasha) were aware of each others' activities during the air war. They studied each other's battle strategies. Both ended up developing "boom-and-zoom" tactics, attacking swiftly from higher altitude to swoop in and blast the enemy at impossibly close range.
There's no record of them actually coming into contact with each other, though.
Hartmann has a story:
>It should be said that the Soviets knew who we were by name. We knew a lot of their pilots, too. I knew of Pokryshkin, Morosov, Litvyak, and the like. Barkhorn and I were in the fight where Litvyak was killed, it seems. The date seems correct, as does the location. But I never claimed that victory.