Observation of a second-order distortion in Nd3Co4Sn13

Abstract In this paper we report the resistivity and neutron scattering experiments on Nd 3 Co 4 Sn 13 . These results indicate that Nd 3 Co 4 Sn 13 undergoes a structural distortion from a high-temperature primitive cubic unit cell to an I -centered superstructure and a concomitant doubling of the lattice constant. The P m -3 n structure of Yb 3 Rh 4 Sn 13 describes well the neutron powder diffraction pattern collected at room temperature, but failed to fit the low–temperature profiles due to the presence of ( h /2 k /2  l )-type diffraction peaks. Single crystal elastic neutron scattering performed in the [ h h l ] scattering plane shows the lattice distortion with mean field character at 124 (2) K as the temperature is lowered. Besides, three I -centered space groups are excluded by the single crystal diffraction work, including I -4 3 d symmetry which is observed in other R 3 T 4 Sn 13 compounds.