Anisotropic resistivity and thermopower of the organic superconductor (ET)2Cu[N(CN)2]Br

We have measured the temperature dependence of the resistivity of (ET)2Cu [N(CN)2]Br in three crystallographic directions and the thermopower in the a and c directions. The resistivity has two maxima - at 75 and 95 K. The value of the resistivity anisotropy is rather large: ρb/ρa is about 103 at the ambient temperature and increases with lowering temperature below 50 K. The temperature derivative of resistivity exhibits a strong maximum at 50 K. Thermopower is positive for the a direction, while it is negative for the c direction. We have concluded, that (ET)2Cu[N(CN)2]Br undergoes insulator-metal transition near 50 K similarly to (ET)2Cu(NCS)2. (orig.)