[en] Polycrystalline samples of (CuIn)_x(AgIn)_yMn_2zTe₂ alloys are used in lattice parameter, optical energy gap E₀, and differential thermal analysis (DTA) measurements and for various sections of constant x/y ratio, T(z) diagrams are determined. The results indicate that for both the zincblende and chalcopyrite phases, ordering of the manganese occurs in the lower temperature range. In contradiction of previous data, it is shown that at temperatures of 200 ⁰C and below, the ordered chalcopyrite α' is the equilibrium condition over the complete range of solid solubility in the adamantine structures. It is shown that the manganese ordering has negligible effect on the lattice parameter but that appreciable lattice parameter differences can occur with different annealing temperatures, these differences being attributed to changes in non-stoichiometry. However, the value of E₀ is appreciably affected by the manganese ordering and it is shown that E₀ gives a very convenient indication of the particular phase present in a single phase sample. (author)