Unusual low-temperature properties of Ce compounds

Low-temperature properties of Ce-based ternary compounds are reviewed. The groundstate of 4f electrons from Ce exhibits a wide variety of unusual features, including magnetic ordering, nonmagnetic or superconductive heavy-fermion state, valence fluctuation, etc. Especially we will concentrate on the equi-atomic series CeTIn and CeTSn (T: transition element), of which the unusual properties will be discussed in terms of competition between the Kondo effect and the indirect RKKY interaction among Ce spins. CeNiSn is a specially interesting example which has a small energy gap growing at low temperature, probably due to coherence effect of heavy quasiparticles in the Kondo lattice. (orig.)