ANISOTROPIC EFFECTS IN THE ANTIFERROMAGNETIC KONDO COMPOUND CEPTSN

The magnetic. transport and thermal properties are reported on a single crystal of CePtSn which is isostructural with the Kondo semiconductor CeNiSn. The Ce ions in CePtSn are trivalent with 4f states governed by a strong crystal field causing an overall splitting of about 500 K. The Kondo effect is manifest by the double-peak structure of the magnetic part of the resistivity rho(m)(T) possessing maxima at 10 and 140 K. Below the antiferromagnetic transition at 7.5 K, another transition appears in both the specific heat C(T) and rho(m)(T) at 5.0 K. A metamagnetic transition occurs in magnetic fields around 9 and 11 T applied along the a and b axes, respectively. A magnetic phase diagram is presented based on the combined results of the field dependence of C(T) and the temperature dependence of the metamagnetic transition. These results are discussed in connection with the problem of the gap formation in CeNiSn.