  In the present work, we calculate the transport coefficients for a
relativistic binary mixture of diluted gases of hard-sphere particles. The gas
mixture under consideration is studied within the relativistic Boltzmann
equation in the presence of a gravitational field described by the isotropic
Schwarzschild metric. We obtain the linear constitutive equations for the
thermodynamic fluxes. The driving forces for the fluxes of particles and heat
will appear with terms proportional to the gradient of gravitational potential.
We discuss the consequences of the gravitational dependence on the driving
forces. We obtain general integral expressions for the transport coefficients
and evaluate them by assuming a hard-sphere interaction amongst the particles
when they collide and not very disparate masses and diameters of the particles
of each species. The obtained results are expressed in terms of their
temperature dependence through the relativistic parameter which gives the ratio
of the rest energy of the particles and the thermal energy of the gas mixture.
Plots are given to analyze the behavior of the transport coefficients with
respect to the temperature when small variations in masses and diameters of the
particles of the species are present. We also analyze for each coefficient the
corresponding limits to a single gas so the non-relativistic and
ultra-relativistic limiting cases are recovered as well. Furthermore, we show
that the transport coefficients have a dependence on the gravitational field.

Statistical Mechanics