Transport, thermal and magnetic properties of the new ternary compound U₃Pd₂₀Si₆: Possibility of a new localized 5f electrons system

We have succeeded in growing the single crystal of a new ternary intermetallic uranium compound U₃Pd₂₀Si₆. It crystallizes in the Cr₂₃C₆-type cubic structure and the uranium ions are located on two different crystallographic sites. Two sucessive magnetic phase transitions are found at 19 K and 2 K in the electrical resistivity, specific heat and magnetic susceptibility measurements. These are attributed to antiferromagnetic and ferromagnetic orderings, respectively. The magnetic susceptibility obeys the Curie-Weiss law above about 50 K with the effective moment 3.30 μ_B/U and the magnetic entropy at 19 K is about RIn3 per uranium ion. These results indicate that the 5f electrons in U₃Pd₂₀Si₆ are likely to be localized. We discuss the magnetic properties of U₃Pd₂₀Si₆ in comparison with those of R₃Pd₂₀X₆ (R=rare earth: X = Si, Ge).