Peculiar behaviors of thermal conductivity, thermal diffusivity and specific heat of high-T-c superconductors near T-c

The thermal conductivity of YBa2Cu3O7-delta single crystals is measured for the first time both in the ab plane (kappa(ab)) and along the crystal axis c (kappa(c)) at temperatures between 4 and 300 K. The dependence kappa(c)(T) exhibits no anomalies due to electron-phonon interaction which are typical of HTSC near T-c and below. The thermal conductivity of a silver-doped yttrium ceramics displays some anomalies near T-c which may be attributed to the effect of superconducting fluctuations.