Magnetic and Fermi surface properties of the ferromagnetic compound UGa₂

We have studied the magnetic and Fermi surface properties in a ferromagnet UGa₂. The electrical resistivity, elastic constant, thermal expansion coefficient, thermoelectric power, magnetic susceptibility and Hall coefficient indicate highly anisotropic properties, reflecting the hexagonal structure. The 5f²- and 5f³-CEF schemes, based on the localized 5f-electron nature, are discussed to understand the magnetic susceptibility and magnetization data. We have also done the magnetoresistance and de Haas-van Alphen (dHvA) experiments to investigate the Fermi surface properties. Both data are very complicated, implying that the Fermi surface is a multiply-connected one. They are explained neither by the localized 5f²- and 5f³-core models nor by the spin-polarized 5f-itinerant model. The cyclotron mass is, however, rather light, ranging from 0.17 to 6.2m₀, which is consistent with the electronic specific heat coefficient of 11 mJ/K²-mol.