The anomalous low temperature lattice thermal conductivity of Nb3Sn and Nb3Al

The thermal conductivity was measured at temperatures in the range approximately 2 - 27 K for arc-melted samples of the β-W-type compounds Nb3Sn and Nb3Al. The samples had relatively high electrical resistivities, and the electronic carrier contribution to the thermal conductivity was correspondingly small, allowing the lattice component of the thermal conductivity to be estimated fairly unambiguously. Both samples exhibited atypical variations in the lattice thermal conductivity, with distinct anomalies occurring at temperatures of approximately 14 K and 10 K for Nb3Sn and Nb3Al respectively. This behaviour apparently correlates with the anomalous heat capacity and intrinsic resistivity variations observed previously for these materials. (Auth.)