Crystal Structure and Physical Properties of NpRh2Sn, a New Np-Based Ternary Compound

We report on the synthesis and physical characterization of a new compound, NpRh2Sn, prepared by arc-melting under argon atmosphere. Rietveld analysis of the powder x-ray diffraction pattern reveals an orthorhombic, UPd2Sn-type structure, with lattice parameters that are the shortest among the AnT2Sn series (An= U, Np, Pu, and T = Pd, Rh). A fit of the high-temperature magnetic susceptibility curve, ¿(T) gives a Curie-Weiss temperature TCW=-29K, and an effective magnetic moment µeff=2,42µB, close to the value expected for Np+3 (2,68µB). The stabilization of antiferromagnetic order below TN=34K is revealed by a cusp in ¿(T) and by a small anomaly in the specific heat curve, Cp(T). An enhanced value of the Sommerfeld coefficient, ¿=107 mJ/Np-mol K2, indicates a moderate heavy-fermion state. NpRh2Sn is the first member of the ANRh2S family, and a rare representative of heavy-fermion systems amidst Np-intermetallics.JRC.DG.E.6-Actinides researc