COMPETITION BETWEEN THE COLLECTIVE SOLIDIFICATION AND SINGLE-PARTICLELOCALIZATION IN THE 2D ELECTRON-SYSTEM

The critical boundary between insulating and metallic phases in 2D ele ctron system in Si was studied vs. temperature and magnetic field. We found a transition from the single-particle localization to collective solidification with temperature, as T --> 0, and with lowering disord er. The critical boundary for the collective transition exhibits quant um oscillations in magnetic field. This results in the reentrant metal -insulator transitions at fixed electron density and varying magnetic field.