  This study investigated the magnetic field ($H$) dependence of thermal
conductivity ($\kappa$) in type I (Pb) and type II (Nb) superconductors. The
$\kappa$ of Nb displayed hysteresis, showing a local minimum during increasing
$H$ process but not during decreasing $H$ process. Different magnetic field
dependencies were observed in Pb with varying purity: $\kappa$ of 3N-Pb
exhibited broad hysteresis, while that of 5N-Pb showed hysteresis similar to
3N-Nb.
