  We have observed commensurability oscillations (CO) in the Hall resistance
$R_{yx}$ of a unidirectional lateral superlattice (ULSL). The CO, having small
amplitudes ($\sim$ 1 $\Omega$) and being superposed on a roughly three-orders
of magnitude larger background, are obtained by directly detecting the
difference in $R_{yx}$ between the ULSL area and the adjacent unmodulated
two-dimensional electron gas area, and then extracting the odd part with
respect to the magnetic field. The CO thus obtained are compared with a
theoretical calculation and turn out to have the amplitude much smaller than
the theoretical prediction. The implication of the smaller-than-predicted CO in
$R_{yx}$ on the thermoelectric power of ULSL is briefly discussed.
