  Local and nonlocal differential resistance measurements on Hall bars defined
in AlO$_x$/KTaO$_3$ heterostructures show anomalous behavior that depends on
the crystal orientation and the applied back gate voltage. The local
differential resistance is asymmetric in the dc bias current, with an
antisymmetric component that grows with decreasing gate voltage. More
surprisingly, a large nonlocal differential resistance is observed that extends
between measurement probes that are separated by 100s of microns. The potential
source of this anomalous behavior is discussed.
