This papers presents the results of the inuence of a weak magnetic eld (MF) (0.354 T) on the electrophysical properties of surface structures based on p-Si. A 300-hours exposure of singlecrystal silicon samples in a magnetic eld stimulates the decay of hydrogen-containing and oxygencontaining surface complexes (ÑHX , SiOH, ÎÍ) and the formation of SiH3 centers. As a result, the surface resistance increases and the barrier properties of the BiSi(p) contact deteriorate