Thermal conductivity measurements in the cuprates have established two unus
ual and distinct features of quasi-particle transport in the superconductin
g state. Both these features (i.e. the abrupt increase in the relaxation ti
me at the onset of superconductivity and a finite zero-energy transport due
to presence of nodes in the superconducting gap) may also be present in ka
ppa - (ET)(2)Cu(NCS)(2) according to the first study of heat transport in t
his two-dimensional organic superconductor. In the case of optimally-doped
Bi-2212, the modification of low-temperature thermal conductivity by the in
troduction of point defects was investigated. Results provide new informati
on on the structure of low-energy electronic excitations of the superconduc
ting state.