  We report on magnetic field dependence of half-integer quantized conductance
plateaus (HQPs) in InAs quantum wires. We observed HQPs at zero applied
magnetic field in InAs quantum wires fabricated from a high-quality InAs
quantum well. The application of in-plane magnetic field causes Zeeman
splitting of the HQP features, indicating that the origin of the observed HQP
is not spontaneous spin polarization. Additionally we observe that conductance
of the split HQPs decreases gradually as the in-plane magnetic field increases.
We finally assume electron-electron interaction as a possible mechanism to
account for the zero-field HQPs and the anomalous field dependence.
