The samples of cobalt monosilicide CoSi and its alloys with the substitution of iron or nickel for cobalt (Co$_1-x$M$_x$Si, M=Fe, Ni) were studied. The investigation were made for alloy compositions with iron content up to 10 at. % and nickel up to 5 at. %. The thermopower and electrical resistivity were measured in the temperature range of 100 – 800 K. Recent calculations of the cobalt monosilicide band structure revealed a number of essential differences from the standard semimetallic model with energy overlap of parabolic bands for electrons and holes. This raises the question on the effect of the new band structure features on the theoretical interpretation of experimental properties of the compound. We analyze the possibility of theoretical interpretation of temperature and concentration dependences of the thermopower and electrical resistivity using different models of the electron spectrum.

The  results  of  investigating  the  thermoelectric  properties of the bulk р -type oxyselenides Bi_1 –_ x Pr_ x CuSeO ( x = 0, 0.04, 0.08) and Bi_0.96La_0.04CuSeO obtained by the solid-state reaction technique are presented. The temperature dependences of the thermopower, electrical resistivity, and thermal conductivity are measured at temperatures from room temperature to 800 K. Over the whole temperature range, a decrease in the electrical resistivity and thermopower is observed with increasing substitution level, while the thermal conductivity is almost unaffected by the substitution of rare-earth elements for bismuth. Despite the nominal valence of Bi, La, and Pr being the same, the replacement of bismuth by rare-earth ions leads to an increase in the charge-carrier concentration, which may be caused by a difference in the electronic configurations of ions, resulting in a shift of the Fermi level to the valence band.