  We present the first observation of instability in weakly magnetized,
pressure dominated plasma Couette flow firmly in the Hall regime. Strong Hall
currents couple to a low frequency electromagnetic mode that is driven by
high-$\beta$ ($>1$) pressure profiles. Spectroscopic measurements show heating
(factor of 3) of the cold, unmagnetized ions via a resonant Landau damping
process. A linear theory of this instability is derived that predicts positive
growth rates at finite $\beta$ and shows the stabilizing effect of very large
$\beta$, in line with observations.
