where R ∞ is the reflectance of an infinitely thick medium, h is Planck's constant, ν is the photon frequency, and γ = 1/2 for a direct transition. Figure shows the direct band gap calculation for Ag 3 Au(Se,Te) 2 . The absorption band edge was estimated by the intersection of the baseline and fitted line, accounting for the non-flat baseline of the Tauc plot. The slope of the Tauc baseline was adjusted to align to improve band gap estimation and visual comparison. The raw, unmodified Tauc plots are provided in Figure . The estimated absorption band edge of alloys ranged between 0.9 eV (Ag 3 AuSe 2 ) and 0.6 eV (Ag 3 AuTe 2 ) and are plotted in Figure . The electronic trend showed a linear pattern with a slight upward curve.