(a) X-ray diffractograms (20° ≤ 2θ ≤ 65°) recorded at different temperatures during in situ annealing from 30 °C to 550 °C, (Mg₃Sb₂: stars, Ag₃Sb: diamonds, α-MgAgSb, β-MgAgSb, and γ-MgAgSb are shown by their symbols). (b) Normalized intensities of the peaks (Ag₃Sb(020): diamonds, Mg₃Sb₂(002): stars, α-MgAgSb(110), β-MgAgSb(022), and γ-MgAgSb(022) as a function of temperature, during in situ annealing. Inset: schematic of the stack: Ag_0.75Sb_0.25/Sb/Mg/SiO₂/Si.