Physical properties of RE3TMSb5 (RE = La, Ce; TM = Ti, Zr, Hf)

Single crystals of RE3TMSb5 (RE = La, Ce; TM = Ti, Zr, Hf) have been grown by Sn flux and characterized by magnetization, electrical resistivity, and specific heat measurements. Powder X-ray diffraction analysis indicates that the title compounds crystallize into the hexagonal Hf5Sn3Cu-type structure (P63/mcm). The physical property measurements for Ce-containing compounds clearly indicate an antiferromagnetic ordering around 5 K. The effective magnetic moment estimated from magnetic susceptibility measurements is close to the theoretical value, indicating the 4f-electrons of Ce3+ ions are well localized. Magnetization isotherms at T = 2 K show anisotropic behaviour between H||ab and H||c. The temperature-dependent electrical resistivity follows a typical Kondo lattice behavior associated with thermal population of crystalline electric field (CEF) levels. The specific heat measurement for Ce-containing compounds reveals a large Cm/T value at low temperatures, which is much bigger than that of La-containing samples. At high temperatures, the CEF energy level scheme is analyzed by fitting to the Schottky peak observed in specific heat, from which the energy splitting levels between the three doublet states are found to be 165 and 380 K for all three Ce-containing samples. The resistivity measurements for all La-containing samples indicate an anomalous broad peak structure at high temperatures. We also investigate the previously reported superconductivity observed in La3TiSb5 and Ce3TiSb5 below 4 K. Our resistivity and specific heat measurements show that the superconductivity is not an intrinsic property of the single crystals, and is attributed to residual Sn flux.