Abstract Single-crystal X-ray diffraction experiments have been performed on KC 24 and RbC 24 in order to study the influence of temperature on the ordering of the alkali metal layers from 300K to 20K. Some important and new data are briefly reported here. In particular, the 95K transition of KC 24 is found to correspond to the breaking of the 2D hexagonal symmetry of the K layer. In contrast, this symmetry is preserved in RbC 24 below the 160K ordering transition and down to 20K. A strong intermodulation with the graphite potential generates satellites reflections which are visible up to the third-order.