  We examined the magneto-transport behavior of electrons confined at the
conducting LaAlO3/SrTiO3 interface in the low sheet carrier density regime. We
observed well resolved Shubnikov-de Haas quantum oscillations in the
longitudinal resistance, and a plateau-like structure in the Hall conductivity.
The Landau indices of the plateaus in the Hall conductivity data show spacing
close to 4, in units of the quantum of conductance. These experimental features
can be explained by a magnetic breakdown transition, which quantitatively
explains the area, structure, and degeneracy of the measured Fermi surface.
