Chiral-crystal-structure transformations and magnetic states of R3Rh4Sn13 (R=La and Ce)

Structural studies were performed on R3Rh4Sn13 (R=La and Ce). X-ray diffraction measurements on single-crystalline samples of both Rh-based compounds, which were synthesized by the molten Sn-flux method, have revealed structural transformations below TD≃ 350 K. The low-temperature superstructures are characterized by the wave vector q=(1/2,1/2,0). The space group in the low-temperature phases of both compounds is chiral cubic I213, which is the same as that of R3Co4Sn13 (R=La and Ce). Neutron diffraction measurement of Ce3Rh4Sn13 revealed no magnetic long-range order below the temperature of the specific-heat peaks at 1.2 and 1.8 K. The low-temperature magnetic state in the chiral phase is that of a paramagnetic semimetal, whereas the dynamical spin correlation of Ce is deduced from the specific-heat data, as found previously in Ce3Co4Sn13.