## 2 Materials and Methods  
Powder samples of CuCr\({}_{2.x}\)Sn\({}_{x}\)S\({}_{2.3}\)Se\({}_{1.7}\) and CuCr\({}_{2.x}\)Sn\({}_{x}\)S\({}_{1.7}\)Se\({}_{2.3}\) were prepared by directly combining high-purity elemental powders (99.99%, Aldrich) in stoichiometric amounts (\(\sim\)0.5 g of the compound). Firstly, powders were mixed manually in hexane with \(\sim\)5 wt% excess of S and Se in an agate mortar and pestle. Hexane was selected to prepare a more homogenous mixture. Then, mixed powders were pressed into disc pellets at \(\sim\) 10 kPa, sealed in evacuated quartz ampoules, and placed in a horizontal tubular programmable furnace. All processes were carried out in an Ar atmosphere. The ampoules were slowly heated from RT to 500 \({}^{\circ}\)C at a rate of 150 \({}^{\circ}\)C/h and maintained at this temperature for 2 h, then were heated to 850 \({}^{\circ}\)C at a rate of 60 \({}^{\circ}\)C/h and kept for 10 days. Finally, the ampoules were gradually cooled to RT at a rate of 60 \({}^{\circ}\)C/h. The resulting powder was annealed and pressed into a pellet, then heated at 850 \({}^{\circ}\)C for 7 days with a 60 \({}^{\circ}\)C/min heating and cooling rate to RT. A similar procedure and stoichiometric amount (\(\sim\)300 mg of the compound) with \(\sim\)5 wt% excess of Se was used to obtain single-crystal. The ampoules were gradually cooled at 10 \({}^{\circ}\)C/h until RT. Single-crystal X-ray diffraction (XRD) data for CuCr\({}_{1.1}\)Sn\({}_{0.9}\)S\({}_{2.3}\)Se\({}_{1.7}\) were accumulated at 293 K with a D8 Venture Bruker AXS diffractometer equipped with Mo K\(\alpha\) radiation (\(\lambda\) = 0.71073 A). Data were accumulated using the Bruker SMART software package [25]. Structural refinement was performed using the SHELXL [26] and Olex2 [27] programs. Powder XRD (PXRD) patterns were collected at RT in the range of 5\({}^{\circ}\) < 20 \(<\) 80\({}^{\circ}\) using a BrukerD8 Advance powder diffractometer (Bruker, Billerica, MA, USA) with Cu K\(\alpha\) radiation (\(\lambda\) = 1.54178 A). The XRD patterns were indexed using the CHEKCLL software [28]. The data were analyzed using Rietveld refinements performed in the MAUD program [29]. A LaB\({}_{6}\) powder standard was used to determine the instrumental profile. Chemical composition determination and mapping analyses of the samples were performed by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) using a Tescan Vega 3 scanning electron microscope equipped with a Quantax 400 EDS microanalyzer. Cylindrical pellets (6 mm in diameter and \(\sim\)2 mm thick) were uniaxially pressed at approximately 5 \(\times\) 10\({}^{8}\) Pa. These samples were then mounted on double-sided carbon tape and adhered to an Al specimen holder for analysis. A Perkin-Elmer Lambda 20 UV/Vis spectrophotometer equipped with a Labsphere RSA-PE-20 diffuse reflectance accessory was used to measure the diffuse reflectance. Raman scattering measurements were conducted on a WITec alpha300 System using 532 nm wavelength excitation. The spectrometer was calibrated with a reference single-crystal Si sample (Raman peak at 520.7 cm\({}^{-1}\)). The spectral data were collected at room temperature in a backscattering configuration in the spectral range of 100-450 cm\({}^{-1}\), with a laser spot of \(\sim\)1 \(\upmu\)m and laser power of 2 mW. The thermal analyses were performed using a Netzsch STA 449 F3 Jupiter apparatus with a heating rate of 10 K-min\({}^{-1}\). Hall-effect measurements were performed using an ECOPIA HMS 2000 system. The pellets for electrical measurements were uniaxially pressed at approximately 2.5 tons, resulting in cylindrical pellets with a 9.00 mm diameter and thicknesses ranging from 0.93 to 1.30 mm. The Hall coefficient, \(\pm\)0.556 T, was obtained from the linear fit of the Hall resistivity. The electrical conductivity was measured using the van der [PERSON] method at RT.