  We report observation of spin-orbit Berry's phase in the Aharonov-Bohm (AB)
type oscillation of weak field magnetoresistance in an anti-dot lattice (ADL)
of a two-dimensional hole system. An AB-type oscillation is superposed on the
commensurability peak, and the main peak in the Fourier transform is clearly
split up due to variation in Berry's phase originating from the spin-orbit
interaction. A simulation considering Berry's phase and the phase arising from
the spin-orbit shift in the momentum space shows qualitative agreement with the
experiment.
