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 intermetal lic uranium compound U3Pd20Si6. It crystallizes in the Cr23C5-type cubic st ructure 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 me asurements. These are attributed to antiferromagnetic and ferromagnetic ord erings, respectively. The magnetic susceptibility obeys the Curie-Weiss law above about 50 K with the effective moment 3.30 mu(B)/U and the magnetic e ntropy at 19 K is about R ln 3 per uranium ion. These results indicate that the 5f electrons in U3Pd20Si6 are likely to be localized. We discuss the m agnetic properties of U3Pd20Si6 in comparison with those of R3Pd20X6 (R=rar e earth: X = Si, Ge).