Electronic structures of rare-earth ternary compounds CePtSb and LaPtSb

The optical conductivity spectra were obtained from a single crystal with ab-plane and ac-plane of CePtSb and polycrystals of CePtSb and LaPtSb. The carrier concentrations in ac-plane and nb-plane were estimated to be 0.042 and 0.182 per molecule from intraband transition, respectively, which is consistent with the result of electrical resistivity. From analysis of interband transitions, the 4d state of Pt-ion in ac-plane lies at about 1.1 eV lower energy than that in ab-plane while the 4f state of Ce-ion lies about 2.8 eV higher energy. The energy shift of these band causes the anisotropy of carrier concentration.