  We have measured the resistivity and the Seebeck coefficient of a MgB2
sintered sample. The temperature dependence of resistivity is fitted well by a
generalized Bloch-Gruneisen equation with a Debye temperature of 1050 K. The
Seebeck coefficient is given by the sum of a diffusive and a phonon drag term
and the behavior in the temperature region $% Tc<T<0.1\Theta_{R}$ follows a
relationship $AT+BT^{3}$ where the two terms are proportional to the electron
and to the phonon specific heat, respectively. The phonon drag term, here
emphasized for the first time, is rather large, indicating a strong
electron-phonon interaction. The diffusive term is positive and increases with
Al doping. The comparison of the experimental values with calculations
including precise electronic structure suggests that $\sigma $ bands give the
main contribution to the Seebeck effect.
