Evidence for a second-order phase transition around 350 K in Ce3Rh4Sn13

We report an observation of a phase transition in Ce3Rh4Sn13 with the transition temperature T∗≃350 K by means of synchrotron x-ray powder diffraction, specific heat, electrical resistivity, Seebeck coefficient, thermal conductivity, as well as Sn119 nuclear magnetic resonance (NMR) measurements. The phase transition has been characterized by marked features near T∗ in all measured physical quantities. The lack of thermal hysteresis in the specific heat indicates a second-order phase transition in nature. From the NMR analysis, the change in the transferred hyperfine coupling constant for two tin sites has been resolved. The obtained result has been associated with the reduction in the averaged interatomic distance between Ce and Sn atoms, particularly for the Sn2 atoms. It indicates that the movement of the Sn2 atoms, which deforms the high-temperature structure, shortens the Ce-Sn2 bond length at low temperatures. We therefore provide a concise picture that the observed second-order phase transition at T∗ of Ce3Rh4Sn13 should be characterized by a structural modulation essentially due to lattice distortions arising from phonon instability.