  The properties of hot matter are studied in the frame of the relativistic
Brueckner-Hartree-Fock theory. The equations are solved self-consistently in
the full Dirac space. For the interaction we used the potentials given by
Brockmann and Machleidt. The obtained critical temperatures are smaller than in
most of the nonrelativistic investigations. We also calculated the
thermodynamic properties of hot matter in the relativistic Hartree--Fock
approximation, where the force parameters were adjusted to the outcome of the
relativistic Brueckner--Hartree--Fock calculations at zero temperature. Here,
one obtains higher critical temperatures, which are comparable with other
relativistic calculations in the Hartree scheme.
