Mechanism of the Giant Magnetoresistance in UNiGa from First-Principles Calculations

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The giant magnetoresistance (MR) in UNiGa is investigated from first principles, using density-functional band-structure theory in the local approximation together with a linear-response ansatz for the conductivity. The MR is calculated to be very anisotropic, with a large value of $\ensuremath{-}(45\ifmmode\pm\else\textpm\fi{}5)%$ for current in plane and a giant MR of $\ensuremath{-}(64\ifmmode\pm\else\textpm\fi{}5)%$ for current perpendicular to plane. These values are in semiquantitative agreement with the measured MR. The basic mechanism of the giant MR is identified to be a superzone reconstruction of the Fermi surface at the field induced metamagnetic transition.