  Temperature-driven metal-insulator and pressure-driven insulator-metal
transitions observed in(BEDT-TTF)8[Hg4X12(C6H5Y)2]] with X = Y = Br are studied
through band structure calculations based on X-ray crystal structure
determination and Shubnikov-de Haas (SdH) oscillations spectra, respectively.
In connection with chemical pressure effect, the transition, which is not
observed for X = Cl, is due to gap opening linked to structural changes as the
temperature decreases. Even though many body interactions can be inferred from
the pressure dependence of the SdH oscillations spectra, all the data can be
described within a Fermi liquid picture.
