Abstract: An alloy having variable spectral reflectance having a composition which essentially consists of Ag, 30 to 46 wt % of Zn and 0.1 to 15 wt % in total of at least one element selected from elements of groups Ia, IIa, Iva, Va, VIa, VIIa, VIII, Ib to Vb and rare earth elements, the alloy being able to have different crystal structures, one of which is obtained when it is held in solid state at a first temperature above the room temperature, another of which is obtained when the same is held in the solid state at a second temperture lower than said first temperature. Disclosed also is an information recording medium made of the alloy. The alloy exhibits a reversible change in color or spectral reflectance as a result of change between two crystal phases, so that the information recording medium produced from this alloy can be used effectively as the medium for recording, regeneration and erasion of the informations.