On heating, amorphous Ag3.1In3.7Sb76.4Te16.5 crystallizes at 416 K in an A7 structure type with atomic sites randomly occupied by the four constituent elements. At 545 K the compound decomposes into two crystalline phases: AgInTe2 is stable up to the melting point, while Sb89Te11 has a modulated layer structure with a temperature-dependent layer period.