K(sub)2MM'(sub)3Se(sub)6 (M=Cu, Ag; M'=Ga, In), a new series of metal chalcogenides with chain--sublayer--chain slabs: infinity(sup)1[M'Se(sub)4]--infinity(sup)2[MSe(sub)4)(M'Se(sub)4)]--infinity(sup)1[M'Se(sub)4]

Synthesis of a new series of quaternary metal chalcogenides containing group 13 elements by a reactive flux method is described. The energy band gaps are larger than those of chalcopyrites. The compounds are capable of absorbing solar radiation and lack infrared absorption property.