  We have measured highly visible Aharonov-Bohm (AB) oscillations in a ring
structure defined by local anodic oxidation on a p-type GaAs heterostructure
with strong spin-orbit interactions. Clear beating patterns observed in the raw
data can be interpreted in terms of a spin geometric phase. Besides h/e
oscillations, we resolve the contributions from the second harmonic of AB
oscillations and also find a beating in these h/2e oscillations. A resistance
minimum at B=0T, present in all gate configurations, is the signature of
destructive interference of the spins propagating along time-reversed paths.
