The role of the impurity acceptor band on the conductivity of the heavy dopped and compensated MNiSn (M = Ti, Zr, Hf) intermetallic semiconductors was determined. A scheme of the impurity band transformation in the n-ZrNiSn compound dopped with the acceptor impurities was proposed. A simulation of the electronic structure for the Zr_1-xSc_xNiSn solid solution was performed. Magnetic susceptibility oscillations around the transition of conductivity metal-insulator during the change in Zr_1-xSc _xNiSn solid solution composition were first experimentally observed. This transition we account for the Anderson transition. These observed oscillations indicate the existence of the Coulomb gap in impurity band of semiconductor during the change of doping level and compensation.