  We report the discovery of 1RXH J082623.6-505741, a 10.4 hr orbital period
compact binary. Modeling extensive optical photometry and spectroscopy reveals
a $\sim 0.4 M_{\odot}$ K-type secondary transferring mass through a low-state
accretion disk to a non-magnetic $\sim 0.8 M_{\odot}$ white dwarf. The
secondary is overluminous for its mass and dominates the optical spectra at all
epochs, and must be evolved to fill its Roche Lobe at this orbital period. The
X-ray luminosity $L_X \sim 1$-$2 \times 10^{32}$ erg s$^{-1}$ derived from both
new XMM-Newton and archival observations, although high compared to most CVs,
still only requires a modest accretion rate onto the white dwarf of $\dot{M}
\sim 3 \times 10^{-11}$ to $3 \times 10^{-10} M_{\odot}$ yr$^{-1}$, lower than
expected for a cataclysmic variable with an evolved secondary. No dwarf nova
outbursts have yet been observed from the system, consistent with the low
derived mass transfer rate. Several other cataclysmic variables with similar
orbital periods also show unexpectedly low mass transfer rates, even though
selection effects disfavor the discovery of binaries with these properties.
This suggests the abundance and evolutionary state of long-period, low mass
transfer rate cataclysmic variables is worthy of additional attention.
