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Single-crystalline tin-selenide (SnSe) has emerged as a high-performance and eco-friendly alternative to the lead-chalcogens often used in mid-temperature thermoelectric (TE) generators. At high temperature >800 K, the phase transition from <i>Pnma</i> to <i>Cmcm</i> causes a significant rise in the TE figure-of-merit (<i>zT</i>) curve. Conversely, the SnSe TE requires a booster at low temperatures, which allows broader applicability from a device perspective. Herein, a synergy of Cu alloy and Ag-coating is realized through a sequential multi-step synthesis, designed to combine different metal deposition effects. Single-crystalline (Cu₂Se)<i>_x</i>(SnSe)_1−<i>x</i> alloys grown by the Bridgman method were then coated with a thin Ag layer by radio frequency (RF) sputtering, and the interlayer epitaxial film was observed via electric-current assisted sintering (ECAS). Consequently, the thin Ag-coating improves the electrical conductivity (<i>σ</i>) and reduces the thermal conductivity (<i>κ</i>) for (Cu₂Se)_0.005(SnSe)_0.995+Ag alloy, increasing the <i>zT</i> curve at close to room temperature (373 K). The incorporation of multistep addition by ECAS enables tuning of the overall solubility of the alloy, which opens a new avenue to optimize TE performance in anisotropic 2D materials.