Actually, yes he does. [i]Congress[i] has limits in what it can require him to hand over. If they want more, than they have to go to his boss (or, since his boss recused himself, his boss' boss). Of course, if POTUS starts forcing him to release materials in ways that compromise active investigations it could potentially open him up to obstruction of justice charges, which is why his advisors have managed to sit on him and convinced him to not stick his fingers in and start interfering.
He's a hand of the Executive Branch. And the Executive Branch is co-equal with Congress.Government bureaucrats don't get to trump elected officials.