  We have combined the Boltzmann transport equation with an {\it ab initio}
approach to compute the thermoelectric coefficients of semiconductors.
Electron-phonon, ionized impurity, and electron-plasmon scattering rates have
been taken into account. The electronic band structure and average intervalley
deformation potentials for the electron-phonon coupling are obtained from the
density functional theory. The linearized Boltzmann equation has then been
solved numerically beyond the relaxation time approximation. Our approach has
been applied to crystalline silicon. We present results for the mobility,
Seebeck coefficient, and electronic contribution to the thermal conductivity,
as a function of the carrier concentration and temperature. The calculated
coefficients are in good quantitative agreement with experimental results.
