Oscillations of magnetoresistance of 2DEG in a weak magnetic field under   microwave irradiation
  Under microwave irradiation, in 2D electron systems with high filling factors oscillations of longitudinal magnetoresistance appear in the range of magnetic fields where ordinary SdH oscillations are suppressed. An unusual beat-like behaviour of these oscillations in weak magnetic fields (B < 0.02 T) was attributed to the zero spin splitting previously. We propose an alternate explanation of this beat-like structure on the basis of the Boltzmann kinetic equation, without any reference to the spin-orbit interaction. 
A. E. Patrakov, I. I. Lyapilin