ANISOTROPIC PSEUDOGAP IN CENISN AND CERHSB STUDIED BY A THERMAL-CONDUCTIVITY MEASUREMENT

We have measured the thermal conductivity kappa for CeNiSn, CeNi0.95Ce Ni0.05Sn (M=Co,Cu), and CeRhSb single crystals. The pronounced enhance ment of kappa along the b axis is observed around 5 and 10 K in CeNiSn and CeRhSb, respectively. In CeNiSn, this enhancement is almost compl etely suppressed either by application of magnetic held of 15 T along the a axis, which is the easy axis of magnetization, or by the substit ution of 5% Co and Cu for Ni. These results indicate that the enhancem ent of K along the b axis originates from the opening of the pseudogap in these compounds. On the other hand, the enhancement of K along the a axis in CeNiSn and those along the a and c axis in CeRhSb are much smaller than that along the b axis. These anisotropic behaviors in K r eflect the anisotropy of the gap in these compounds.