High-pressure thermopower of sulfur

First measurements of the thermopower and transverse magnetoresistance of sulfur at ultrahigh pressures of up to similar to40 GPa are reported. The conductivity of sulfur, as that of other elemental Group VI semiconductors (Te, Se), is shown to be due to valence band holes. The variation of band gap width is derived from the pressure dependence of thermopower. The observed negative magnetoresistance of sulfur at P similar to 30 GPa indicates a low hole mobility and suggests the existence of an indirect minimum gap in the electronic spectrum. The pressure-induced variation of the electronic structure of sulfur is discussed in terms of the Peierls lattice instability model. (C) 2003 MAIK "Nauka / Interperiodica".