Thermal conductivity of superconductive Y-Ba-Cu-O

We have measured the thermal conductivity of a superconducting Y-Ba-Cu-O compound as a function of temperature. We find that the thermal conductivity is nearly temperature independent as temperature is lowered below 140 K, but increases sharply at the transition temperature, which is about 85-90 K for our sample. These results can be accounted for by a reduction in phonon-electron scattering below $T_c$ in this material.