  We investigate the phase structure of SU(4) gauge theory with the gauge field
simultaneously coupled to two flavors of fermion in the fundamental
representation and two flavors of fermion in the two-index antisymmetric
representation. We find that the theory has only two phases, a low-temperature
phase with both species of fermion confined and chirally broken, and a
high-temperature phase with both species of fermion deconfined and chirally
restored. The single phase transition in the theory appears to be first order,
in agreement with theoretical predictions.
