Thermal and Electrical Conductivities of Very-High-Purity Indium

Measurements of the thermal and electrical conductivities of a polycrystalline indium sample of very high purity have been performed between 1.5 and 4.2°K and in the presence of longitudinal magnetic fields up to 15 000 Oe. It was found that, within the experimental error, the electrical and thermal Kohler's rules were satisfied, the functional forms for the two being quite similar. The expression for the resistivity as a function of $T$ for the normal state and in zero magnetic field are in good agreement with theory. The Lorenz number obtained by extrapolating to $T=0\mathrm{}$ gives a very high value compared with the theoretical one. Measurements of the thermal conductivity for the superconducting state, in the same temperature range, have been made. The thermal-resistivity ratio $\frac{W_n}{W_s}$ as a function of the reduced temperature does not agree with the results of Kadanoff and Martin.