Anomalous Low-Field Classical Magnetoresistance in Two Dimensions
  The magnetoresistance of classical two-dimensional electrons scattered by randomly distributed impurities is investigated by numerical simulation. At low magnetic fields, we find for the first time a negative magnetoresistance proportional to |B|. This unexpected behavior is shown to be due to a memory effect specific for backscattering events, which was not considered previously. 
Alexander Dmitriev, Michel Dyakonov and Remi Jullien