13C-NMR studies of the ‘narrow gap semiconducting’ state of α-(BEDT-TTF)2I3 under pressure

Single crystal 13 C NMR measurements were carried out at pressures of 0.7 and 1.4 GPa to investigate the unusual high-pressure state of α-(BEDT-TTF) 2 I 3 . Large temperature dependences of susceptibility was observed at 0.7 GPa. However, the temperature dependence of relaxation rate seems to contradict with the rapid drop of carrier density determined by Hall effect measurements at low temperatures. This may require us a serious reconsideration of the nature of the high-pressure phase.