We have observed a novel feature in the hot-electron magnetophonon resonance in n -type germanium at pulsed high magnetic fields up to 40 T. In the longitudinal magnetophonon resonance, the resonance peaks appear as either maxima or minima depending on the difference in the effective mass between the initial and final states of the intervalley scattering by phonons. The results are interpreted in terms of the mobility change of conduction electrons at the resonance.