Charge density wave and superconductivity of RPt₂Si₂ (R = Y, La, Nd, and Lu)

The temperature dependence of electrical resistivity and magnetic susceptibility was studied for RPt2Si2 compounds with R = Y, La, Nd, and Lu. LaPt₂Si₂ and NdPt₂Si₂ show steps in the resistivity vs temperature curve at T* = 112 and 77 K, respectively. We performed X-ray diffraction and selected-area electron diffraction (SAED) measurements for LaPt₂Si₂ at low temperatures. It was found that LaPt2Si2 undergoes a structural transition from tetragonal to orthorhombic at T*. Moreover, (n/3, 0, 0) superlattice reflections with n = 1 and 2 were observed at 10K in the SAED patterns. These results strongly suggest the formation of a charge density wave (CDW) in LaPt₂Si ₂ below T. On the other hand, the compounds R = Y, La, and Lu were found to show superconductivity below 1.5-1.9 K. The origin of a CDW and its coexistence with superconductivity in RPt₂Si₂ are discussed.