generation efficiency, which is characterized by a dimensionless figure-of-merit ZT of the materials employed. ZT is defined as ZT = S 2 σT/(κ e +κ L ), where S, σ, and T are the Seebeck coefficient, electrical conductivity, and absolute temperature, κ e and κ L are thermal conductivity contributed by charge carriers (either electrons or holes) and phonons, respectively. [2] The thermoelectric properties of chalcogenides with weakly bonded 2D atomic sheets, such as SnSe, [3] SnSe 2 , [4] Cr 2 Ge 2 Te 6 , [5] GeSe, [6] and In 4 Se 3[7] are attracting attention because they show intrinsically low thermal conductivities deriving from the layered structure. CuSbSe 2 is also a similar chalcogenide with a direct bandgap of ≈1.0 eV [8,9] and exhibits potential for thin-film photovoltaic applications. [10,11] As shown in Figure 1a, the CuSbSe 2 crystallizes in an orthorhombic structure with the Pnma space group. This material has 2D double-layered honeycomb-like sheets within the ab plane, which is composed of self-condensed Sb 2 CuSe 3 and SbCu 2 Se 3 six-membered rings. [8] The Cu atom is tetrahedrally coordinated to four Se atoms with three kinds of CuSe bonds, while the Sb atom is coordinated by three Se atoms in a trigonal pyramidal configuration( Figure 1b). The Sb 3+ has lone-pair 5s 2 electrons which are stereochemically expressed in the structure. [12] Such structural features result in giant lattice vibration anharmonicity with a large average Grüneisen parameter γ ave of 1.215, [13,14] which is benifical for low thermal conductivity as found in tetrahedrites, [15,16] AgBiSe 2 , [17,18] CuSbS 2 , [19] and InTe [20] compounds. In addition, the neighboring 2D CuSbSe 2 sheets are interconnected by weaker secondary SbCu and SbSe bonds (pink dotted lines in Figure 1b). [21] The lattice vibration anharmonicity combined with the interlayer weaker bonding leads to low lattice thermal conductivity in the CuSbSe 2 compound, [22] similar to SnSe, [23] AgSbTe 2 , [24] and Cu 3 SbSe 3 . [25] In addition, first-principles density functional theory calculations reveal that the valence bands near the Fermi level of CuSbSe 2 are relatively flat and degenerate at Z point (0, 0, 1/2), which lead to a high effective mass (m*≈ 2.05 m 0 ). [9] Thus, an intrinsically high Seebeck coefficient is also expected in this compound. These attributes as well as the earth-abundant and low-toxic constituent elements make this material worth exploring for This work reports the thermoelectric properties of the CuSbSe 2 -x mol% PtTe 2 (x = 0, 0.5, 1.0, 1.5, and 2.0) pellets composed of highly oriented single crystalline nanoplates. CuSbSe 2 -PtTe 2 single crystalline nanoplates are prepared by a wet-chemical process, and the pellets are prepared through a bottom-up self-assembly of the CuSbSe 2 -PtTe 2 nanoplates and spark plasma sintering (SPS) process. X-ray diffraction and field emission scanning electron microscopic analyses show a highly textured nature with an orientation factor of ≈0.8 for (00l) facets along the primary surface of the p...