Metal to Nonmagnetic-Insulator Transition in LiVS$_{2}$

LiVS$_{2}$ has been reported to exhibit a first order magnetic transition with a drastic decrease in susceptibility at about 310 K$^{[1]}$. In order to clarify the nature of this transition, we performed resistivity, magnetic susceptibility, and electron diffraction measurement for LiVS$_{2}$. The resistivity in LiVS$_{2}$ revealed a metal to insulator (MI) transition at $T_{c} \quad \sim $ 310 K. In the insulating state below $T_{c}$, we observed $\sqrt 3 a_0 \times \sqrt 3 a_0 $superstructure in the electron diffraction, indicating a formation of vanadium trimers in the \textit{ab} plane. Together with the drastic decrease in susceptibility at $T_{c}$, we propose a formation of trimer singlet state below $T_{c}$ for LiVS$_{2}$. Although this ground state is analogous to that observed in the isostructural and isoelectronic oxide LiVO$_{2}^{[2]}$, the MI transition is unique to LiVS$_{2}$. [1] D. W. Murphy \textit{et al.}; Inorg. Chem. \textbf{15} (1976) 17. [2] W. Tian \textit{et al.}; Mater. Res. Bull. \textbf{39} (2004) 1319.