  Weak localization leads to the same correction to both the conductivity and
the electron-phonon coupling constant $\lambda$ (and $\lambda_{tr}$).
Consequently the temperature dependence of the (thermal) electrical resistivity
is decreasing as the conductivity is decreasing due to weak localization, which
results in the decrease of the temperature coefficient of resistivity (TCR)
with increasing the residual resistivity. When $\lambda$ is approaching zero,
only residual resistivity part remains and gives rise to the negative TCR.
Accordingly, the Mooij rule is a manifestation of weak localization correction
to the conductivity and the electron-phonon interaction. This study may provide
a new means of probing the phonon-mechanism in exotic superconductors.
