Hysteretic behavior and magnetic ordering in CeRuSn

We report the thermodynamic and transport properties of the newly synthesized Ce-intermetallic compound CeRuSn. This ternary stannide possesses an unconventional structure with two Ce sites at room temperature which exhibit different valencies. Just below room temperature there are large thermal hysteretic effects in the magnetic susceptibility, in the specific heat, as well as in electronic and heat transport properties suggesting the formation of an incommensurate charge density wave modulation whose q vector changes as a function of temperature. Our measurements indicate that one site displays magnetic Ce3⁺ behavior while the other is a valence fluctuator. At 2.7 K antiferromagnetic long-range order occurs within one-half of the Ce sites, e.g., the magnetic entropy of the transition is 12Rln2. Below T_N a series of metamagnetic transitions takes place in rather small fields (~1-2 T), leaving a magnetically fluctuating background. Such behavior is unique among the many Ce-transition-metal compounds.