Crystal polymorphism in TmPd3S4

Cubic TmPd3S4 is in the series of rare-earth (R) palladium bronzes, RPd3S4, which is an attractive platform for multipolar interaction systems. We previously reported that, in RPd3S4, only TmPd3S4 shows a Jahn–Teller-like phase transition at approximately 200 K, accompanying a structure modulation. Our present electron diffraction study, however, has revealed that the expected modulation does not occur. We reexamined the crystal growth conditions and found crystal polymorphism with the cubic and monoclinic structures. The phase transition at approximately 200 K can be interpreted as a phase separation into the cubic and monoclinic phases. Single-phase monoclinic TmPd3S4 was successfully obtained at room temperature. The monoclinic TmPd3S4 is metallic and shows no magnetic phase transition down to 0.6 K.