Abstract

We calculate the semiclassical magnetoresistivity ρxx(B) of noninteracting fermions in two dimensions moving in a weak and smoothly varying random potential or random magnetic field. We demonstrate that in a broad range of magnetic fields the non-Markovian character of the transport leads to a strong positive magnetoresistance. The effect is especially pronounced in the case of a random magnetic field where ρxx(B) becomes parametrically much larger than its B=0 value.