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High-field galvanomagnetic effects have been investigated in the pyrite structure metallic compound AuSb2 in fields up to 150 kG. The resistance ratios of the samples [ρ(295°K)/ρ(4.2°K)] were as high as 520. The results indicate that AuSb2 is a compensated metal and that its Fermi surface supports open orbits in 〈100〉, 〈110〉, and 〈112〉 directions. At fields higher than about 50 kG, the tendency toward saturation caused by the open orbits changes to a field dependence approaching quadratic, and rather large-amplitude quantum oscillations in the magnetoresistance appear. This behavior is explicable in terms of a loss of the open orbits in the highest fields as a result of magnetic breakdown. An approximate calculation based on the theory of magnetic breakdown gives a value of 85 meV for the size of the energy gaps involved in the breakdown.