The measurements on the temperature dependency of the Seebeck coefficient and resistivity of sintered specimens of uranium monosulfide, thorium monosulfide, and US‐ThS solid solutions indicate semimetallic and metallic behavior for US and ThS, respectively. The thermoelectric power of US exhibits a weak dependence on temperature and decreases with increasing ThS content; except for initial disordering effects, the resistivity of US shows a similar dependence on temperature and composition. The presence of higher sulfides in US results in a considerable lowering of the Seebeck coefficient with increasing temperature. The figures of merit for US are too low for useful high‐temperature power generation by a factor of approximately ten.