At the liquid helium temperature and under application of magnetic fields up to 9,4 T, a voltage drop across a silicon diode with metallic conductivity of the emitter and base has been measured under passing a constant forward current through the diode. Observed magnetoresistance of the diode is proved as a whole to be extremely small, negative at low fields and changing its sign when the field increases. In the positive region of the diode magnetoresistance, its field dependence is quadratic at first and then becomes close to the linear one. With increase in the current through the diode, the negative component of the diode magnetoresistance decreases, and the smaller its value, the more extended is the quadratic section and the shorter is the linear one. The results are interpreted as caused by hopping conduction over a system of electron "lakes" in the region of p - n junction.