GLYPH<s48> GLYPH<s50>GLYPH<s48>GLYPH<s48>GLYPH<s48> GLYPH<s52>GLYPH<s48>GLYPH<s48>GLYPH<s48> GLYPH<s54>GLYPH<s48>GLYPH<s48>GLYPH<s48> GLYPH<s56>GLYPH<s48>GLYPH<s48>GLYPH<s48> GLYPH<s49>GLYPH<s48>GLYPH<s48>GLYPH<s48>GLYPH<s48> GLYPH<s45>GLYPH<s48>GLYPH<s44>GLYPH<s48>GLYPH<s50> GLYPH<s48>GLYPH<s44>GLYPH<s48>GLYPH<s48> GLYPH<s48>GLYPH<s44>GLYPH<s48>GLYPH<s50> GLYPH<s32> GLYPH<s49> GLYPH<s46>GLYPH<s53> GLYPH<s75> GLYPH<s49> GLYPH<s46>GLYPH<s50> GLYPH<s75> GLYPH<s48> GLYPH<s46>GLYPH<s57> GLYPH<s75> GLYPH<s48> GLYPH<s46>GLYPH<s55> GLYPH<s75> GLYPH<s48> GLYPH<s46>GLYPH<s54> GLYPH<s75> GLYPH<s82>GLYPH<s47>GLYPH<s82> GLYPH<s72>GLYPH<s44>GLYPH<s71> GLYPH<s48> GLYPH<s44>GLYPH<s52> GLYPH<s50> GLYPH<s75> FIG. 3: Temperature behavior of magnetoresistance for the structures similar to described at Fig. 2 but with concentration of Be 9 · 10 17 cm − $^{3}$. 31 strongly increases with temperature decrease, ∝ T − 7 / 3 ( Mott law ) , ∝ T − 9 / 4 ( ES law ) (37) In addition, we can expect that for the sample with large n H$_{sat}$ < H$_{min}$ , thus it is H$_{sat}$ which plays a role of H$_{min}$ . Due to weak temperature dependence of R$_{sat}$ the temperature behavior at the fields larger than H$_{sat}$ , that is corresponding to the minimum of ρ ( H ), is completely controlled by the spin PMR which gives ρ ( H ) ∝ T − α with α > 2 . Indeed, an increase of resistance by a factor of 4-5 is observed at the fields larger than 0.3 T for the temperature variation from 0.9 to 0.4 K. To conclude, we have reconsidered existing theory of hopping magnetoresistance. We have shown that the random potential induced by the background impurities can affect the asymptotics of the localized states and, as a result, suppress to some extent the negative magnetoresistance related to interference effects. We have also generalized the theory for the case of acceptor states in 2D structures including the effects of the upper Hubbard band. The results obtained are in agreement with existing experimental data. In particular, we 18 VI. CONCLUSIONS