A new quaternary sul5de, BaLa 2 MnS 5 , was prepared by the reaction of CS 2 with a mixture of BaCO 3 , La 2 O 3 , and MnO 2 at 1323 K. The crystal structure of this compound is tetragonal with space group I4/mcm. The lattice parameters are a โซุโฌ 8.014(2) and c โซุโฌ 13.867(3) A s . The re5nement of the di4raction data was carried out by the Rietveld method yielding (Ba 1/3 ,La 2/3 ) in 4a (0, 0, 1/4) and 8h (0.1620, 0.6620, 0), Mn in 4b (0, 1/2, 1/4), S(1) in 4c (0, 0, 0), and S(2) in 16l (0.1514, 0.6514, 0.6352). The 5nal reliability factors were R wp โซุโฌ 13.22, R p โซุโฌ 9.91, R I โซุโฌ 2.94, and R F โซุโฌ 1.82%. The interatomic distance showed a deviation according to the bonds giving distances longer or shorter than the crystal radius sums, which suggests the existence of some covalency in the crystal. The electrical conductivity and Hall coe7cient were measured using the van der Pauw method in a temperature range from 18 to 300 K. The electrical conductivity was on the order of 10 2 S m ุ1 , and it increased with increasing temperature showing that BaLa 2 MnS 5 is semiconductive. The negative Hall coe7cient indicated that the conduction is n-type. The activation energy of conduction was 16 meV above 200 K.