The effect of high concentrations of acceptor dopants (N _A = 10²⁰ cm^-3) on the electronic structure, Fermi level, electrical conductivity, Seebeck coefficient, and magnetic susceptibility of n-ZrNiSn intermetallic semiconductors is studied. The role of impurity bands produced by donors and acceptors in the conductivity of the heavily doped n-ZrNiSn compound is clarified. The transition from activated conductivity to metal conductivity under variations in the concentration of acceptor dopants is observed.