Monocrystals are synthesized and grown according to Bridgman-Stockbarger method, and the influence of rareearth elements (REE) as well as of γ-irradiation on electrophysical properties of ( ) ( ) 1 SnSe LnSe − − x x ( ) Ln Pr, Tb, Er − alloy system is investigated. During transition from SnSe to ( ) ( ) 1 SnSe LnSe − − x x solid solutions, a partial compensation of charge carriers occurs and additional scattering centres appear. At low temperatures T < 350 K after irradiation with γ-quanta, thermoemf in samples of p-type conduction becomes higher and decreases in those of n-type conduction. In addition, under the influence of γ-rays radiation, defects come into being causing a decrease in lattice heat conduction and a rise in electron heat conduction. REE impurities are supposed to be positioned among the points of crystal lattice during irradiation with γ-quanta and, moreover, Frenkel defects are formed.