The interaction of benzene with ternary GICs MHgC 8 (M = K, Rb) has been investigated and new quaternary compounds MHgC 8 (C 6 H 6 ) 2 were obtained. X-ray data, Fourier transform of 001 reflections and spin-lattice relaxation measurements show that benzene molecules intercalate into the empty galleries of the amalgam GICs.