  We report the discovery of the diatomic molecule SiO in the gas phase in the
environment of the recurrent nova T Coronae Borealis. While some of the SiO is
photospheric, a substantial portion must arise in the wind from the red giant
component of T CrB. A simple fit to the SiO feature, assuming local
thermodynamic equilibrium, suggests a SiO column density of 2.8x10^17 /cm2 and
temperature ~1000K; the SiO column density is similar to that present in the
winds of field red giants. A search for SiO maser emission is encouraged both
before and after the next anticipated eruption. We find that the 12C/13C ratio
in the red giant is <9, with a best fit value of ~5, a factor ~18 times lower
than the solar value of 89. We find no convincing evidence for the presence of
dust in the environment of T CrB, which we attribute to the destructive effects
on nucleation sites of hard X-ray emission. When the next eruption of T CrB
occurs, the ejected material will shock the wind, producing X-ray and coronal
line emission, as is the case for the recurrent nova RS Oph. T CrB is also a
good candidate for very high energy gamma-ray emission, as first observed
during the 2010 outburst of V407 Cyg. We include in the paper a wide variety of
infrared spectroscopic and photometric data.
