  An interplay between the increase in the number of carriers and the decrease
in the scattering time is expected to result in a saturation of the in-plane
resistivity, $\rho_{ab}$, in graphite above room temperature. Contrary to this
expectation, we observe a pronounced increase in $\rho_{ab}$ in the interval
between 300 and 900 K. We provide a theory of this effect based on intervalley
scattering of charge carriers by high-frequency, graphene-like optical phonons.
