Boron isotope effects on the thermoelectric properties of UB4 at low temperatures

The thermoelectric power and electrical resistivity of UB4 with three different boron isotope enrichments were measured in the temperature range from 80 to 300 K. The thermoelectric power of each sample decreased with decreasing temperature, but a slight saturation of the decrease due to phonon-drag effect was observed below 120 K for both boron isotope enriched samples. The resistivity decreased with decreasing temperature and there existed no large difference among the resistivities of natural boron, boron-10 enriched and boron-11 enriched samples. The figure of merit for thermoelectricity of UB4 was lower by three orders of magnitude than that of well-known thermoelectric material (Bi,Sb)2(Te,Se)3.