Anisotropy of thermal conductivity in YBaCuO single crystals

The anisotropy of thermal conductivity (k) in single crystals YBa2Cu3O7 hav e been studied. The temperature dependence of k in c-direction is well desc ribed by the lattice thermal conductivity (T-max=60 K; k(max)=4 W/mK; T-D=1 40 K). The precise measurements reveal the hysteretic behavior of out-of-pl ane thermal conductivity. In ab-direction the upturn in k for temperatures below T-c is observed and temperatures of thermal conductivity peaks in ab- and c-direction are coincided. Theoretical analysis suggests a model in wh ich an observed peak below T-c in thermal conductivity for ab-direction is ascribed to a quasiparticle contribution.