[en] Elastic and inelastic neutron scattering are reported for C₈Rb in the temperature range 4 to 800 K. Several phase transitions above room temperature are reported for the first time; these consist of changes in metal layer stacking and ultimately at 747 K the onset of 2D liquid behavior. Phonon dispersion of LA and LO modes propagating along c imply a 20% increase in the interlayer force constant relative to pure graphite. The zone boundary TA mode softens dramatically with increasing temperature, which may be related to the phase transitions