  We describe a near-IR photometric search for cool red dwarf companions to hot
EUV-detected white dwarfs (WDs). While some composite systems have been found
optically among WDs detected in recent EUV All-Sky Surveys, we develop an IR
technique that probes farther down the main sequence, detecting yet more
companions. We use detailed DA model atmosphere fits to optical spectra to
predict K magnitudes and distances, against which we contrast our near-IR
observations. Our photometric survey reveals 10 DAs with a significant excess
in both J and K. Half are newly discovered, and are most likely previously
unrecognized binary systems. Neither the frequency of infrared excess nor the
mass estimate of the red dwarf companion correlate with white dwarf mass, as
might be expected if either the EUV detectability or mass of the white dwarfs
were significantly affected by a companion. Infrared spectra of these systems
should help to determine the mass and spectral type of the cool companions
presumably causing the IR excess, leading to better estimates of the mass ratio
distribution in binaries.
  Counting previously known binaries, and resolved pairs, we find the total
binary fraction of the sample is at least a third. Since most WD progenitors
had initial masses larger than about 2 solar masses, we thus provide a
photometric measure of the binary fraction of high mass stars that would be
difficult to perform in high mass main sequence stars. We estimate that 90% of
the companions are of type K or later.
