The
pressure dependence of the resistivities of a single-component
molecular conductor, [Ni(hfdt)2] (hfdt = bis(trifluoromethyl)tetrathiafulvalenedithiolate)
with semiconducting properties at ambient pressure was examined. The
four-probe resistivity measurements were performed up to ∼10
GPa using a diamond anvil cell. The low-temperature insulating phase
was suppressed above 7.5 GPa and the resistivity dropped, indicating
the superconducting transition occurred around 7.5–8.7 GPa
with a maximum Tc (onset temperature)
of 5.5 K. The high-pressure crystal and electronic band structures
were derived by the first-principle calculations at 6–11 GPa.
The crystal was found to retain the semiconducting band structure
up to 6 GPa. But the electron and hole Fermi surfaces appear at 8
GPa. These results of the calculations agree well with the observation
that the pressure-induced superconducting phase of [Ni(hfdt)2] appeared just above the critical pressure where the low-temperature
insulating phase was suppressed.