Li 17 Sb 13 S 28 was synthesized by solid-state reaction of stoichiometrica mounts of anhydrous Li 2 Sa nd Sb 2 S 3 .T he crystal structure of Li 17 Sb 13 S 28 was determined from dark-red single crystalsa tr oom temperature. The title compound crystallizes in the monoclinic space group C2/m (no. 12) with a = 12.765(2) , b = 11.6195(8) , c = 9.2564(9) , b = 119.665(6)8, V = 1193.0(2) 3 ,a nd Z = 4( data at 20 8C, lattice constants from powder diffraction). The crystal structure contains one cation site with am ixed occupation by Li and Sb, and one with an antimonys plit position. Antimony and sulfur form slightly distorted tetragonal bipyramidal [SbS 5 E] units (E = free electron pair). Six of these units are arranged aroundavacancy in the anion substructure.T he lone electron pairs E of the antimony(III) cations are arranged around these vacancies. Thus, av ariant of the rock salt structure type with ordered vacanciesi nt he anionic substructure results. Impedance spectroscopic measurements of Li 17 Sb 13 S 28 show as pecific conductivity of 2.9 10 À9 W À1 cm À1 at 323 K and of 7.9 10 À6 W À1 cm À1 at 563 K, the correspondinga ctivatione nergy is E A = 0.4 eV below 403 Ka nd E A = 0.6 eV above. Ramans pectra are dominated by the SbÀSs tretching modes of the [SbS 5 ]u nits at 315 and 341 cm À1 at room temperature. Differentialt hermala nalysis( DTA) measurements of Li 17 Sb 13 S 28 indicate peritectic melting at 854 K.