Influence of hydrogen on the thermal conductivities of superconducting Nb and Ta

The thermal conductivities of superconducting Nb and Ta have been measured in the temperature range 0.04-4 K with and without the presence of dissolved H or D. In Nb doped with D the phonon mean free path exhibits a minimum which occurs at the same temperature at which a deuterium-related anomaly has been observed in the specific heat. Phonon scattering caused by the addition of H to Nb or Ta is complicated by the presence of resonant scattering from dislocations produced by precipitation of the $\beta$-phase hydride.