LAUSR

Abstract We succeeded in growing five new single crystalline compounds RPt 2 Cd 20 (R = La, Ce, Pr, Nd, and Sm) by the Cd self-flux method. These compounds are found to crystallize in the cubic CeCr 2 Al 20 -type crystal structure by the X-ray diffraction using single crystals. We measured the electrical resistivity, magnetic properties, and specific heat for all compounds. The resistivity for R = Ce, Nd, and Sm indicates an abrupt decrease, which might correspond to a magnetic transition. It is suggested that the ground state of CePt 2 Cd 20 is Γ 7 doublet from the magnetization measurement. The magnetization of PrPt 2 Cd 20 shows a metamagnetic behavior at 1.6 T in the paramagnetic state, which could be due to the crystalline electric field effect with non-Kramers Γ 3 doublet or Γ 1 singlet ground state. The contribution of optical phonon modes to the lattice specific heat is discussed in LaPt 2 Cd 20 .