Anomalous magnetoresistance at a mesoscopic bend

We have carried out magnetoresistance measurements on a mesoscopic cross formed from two split gates on a GaAs/AlGaAs 2DEG and have observed anomalous peaks in the bend resistance before the electron collimation is finally destroyed by the magnetic field. We have considered two possible explanations for this effect, and have rejected the possibility of quantum mechanical effects in favor of a classical one in which we postulate the presence of an impurity close to the center of the active region.