Abstract A detailed analysis is presented for 121Sb Mössbauer spectroscopy data obtained from two SbCl 5 .HOPG samples. All spectra exhibit two resonances which are assigned to Sb(+5) (in an undetermined molecular form) and Sb(+3) (present as SbCl 3) with an intensity ratio of approximately 2 : 1. An analysis of the vibrational anisotropy reveals that both species are intercalated. The results are compared with those previously reported for SbF 5 .HOPG. The proper methodology of Mössbauer spectroscopy in such anisotropic and technically thick samples is demonstrated.