13CNMR study of nesting instability inα−(BEDT−TTF)2RbHg(SCN)4

The low-temperature nesting instability in the quasi-two-dimensional organic conductor, ${\mathrm{\alpha }-(\mathrm{B}\mathrm{E}\mathrm{D}\mathrm{T}-\mathrm{T}\mathrm{T}\mathrm{F})\mathrm{}}_2{\mathrm{RbHg}\left(\mathrm{SCN}\right)\mathrm{}}_4,$ has been investigated by ${}^{13}\mathrm{C}$ NMR. Below 12 K, drastic decreases in the Knight shift and ${1/(T}_{1}T)$ were observed with neither splitting nor broadening in the NMR spectra. The ${1/(T}_{1}T)$ shows no enhancement around the nesting instability, unlike the conventional spin-density-wave (SDW) transition. The present ${}^{13}\mathrm{C}$ NMR data are suggestive of nonmagnetic transition but allow only an unusual case of mobile state in the SDW scenario.