To explore the connection between α-(BEDT−TTF) 2 I 3 and α-(BEDT−TTF) 2 MHg(SCN) 4 (M = K, Rb, Tl and NH 4 ) and to resolve the difference between band picture and charge fluctuation of α-(BEDT−TTF) 2 MHg(SCN) 4 , we utilized 13 C-NMR to examine α-(BEDT−TTF) 2 RbHg(SCN) 4 under the conditions with a large hyperfine coupling constant at each site. The temperature dependence of site susceptibility showed the development of spin disproportionation as observed in α-(BEDT−TTF) 2 I 3 . We found that

more »

... he linewidth of the A site only increased as temperature decreased from 200 to 100 K, a change associated with the development of lattice modulation. These findings indicate that density-wave modulation occurs during charge disproportionation instability.