Anisotropy of the upper critical field in ultrahigh-pressure-induced superconductor (TMTTF)2PF6

We have measured the temperature dependence of resistivity of (TMTTF)2PF6 under high pressures up to 7 GPa by using a turnbuckle DAC (diamond anvil cell) for pressurization, also in magnetic field up to 5 T. In superconducting transition, zero-resistivity was successfully observed even there are not many cases that zero-resistivity has been observed from measurements of organics under high pressures. Superconductivity was observed at P=4.18-6.03 GPa and showed the highest TC of 2.25 K at 4.58 GPa. The temperature dependence of the upper critical magnetic field HC2(T) was determined via resistivity at P=4.58 GPa, for the intrachain (a), interchain (b'), and interlayer (c*). Also, the values of GL coherence lengths for three different axis which obtained from this work show that (TMTTF)2PF6 is anisotropic three-dimensional superconductor.