The role of magnetic ions on the magnetotransport properties of the charge-transfer salts β''-BEDT-TTF4[(H3O)M(C2O4)3]C5H5N where M=Ga3+, Cr3+ or Fe3+

We report high-field magnetotransport measurements on β''-BEDT-TTF4[(H3O)M(C2O4)3]C5H5N, where M=Ga3+, Cr3+ or Fe3+. In spite of the differing M ions, these compounds have very similar Fermi surfaces. We observe four distinct Shubnikov-de Haas frequencies, corresponding to four Fermi-surface pockets; the frequencies exhibit the additive relationship expected for a compensated semimetal. The compounds show paramagnetic behaviour and no superconductivity down to 0.5 K, in contrast to other materials of the same family with different solvent molecules