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Quaternary Rare-Earth Arsenides REAg 1-xZnyAs2 (RE: La-Nd, Sm, Gd-Dy) with Tetragonal SrZnBi 2-and HfCuSi2-Type Structures. -The title compounds are prepared from stoichiometric mixtures of the elements (silica tubes, 800 C, 20 d) and characterized by powder and single crystal XRD, magnetic measurements, and TB-LMTO-ASA band structure calculations. LnAg0.5Zn0.5As2 (Ln: La, Ce) crystallize in the space group I4/mmm with Z = 4 (SrZnBi 2-type structure). LnAg0.5Zn0.5As2 (Ln: Pr, Nd, Sm, Gd, Tb, Dy), NdAg 0.8Zn0.2As2, NdAg0.6Zn0.4As2, NdAg0.4Zn0.5As2, and NdAg0.2Zn0.6As2 crystallize in the space group P4/mmm with Z = 2 (HfCuSi2-type structure). The Ag and Zn atoms are disordered within metal-centered tetrahedra, which share edges to form [MAs] (M: Ag, Zn) layers that are fragments of the PbO-type structure. The substitution of Zn in stoichiometric ternary arsenides LnAgAs 2 results in nonstoichiometric quaternary arsenides LnAg 1-xZnyAs2 in which the combined Ag and Zn content can become less than unity as in the Nd-containing series. PrAg 0.5Zn0.5As2 and NdAg 0.5Zn0.5As2 are paramagnetic. -(RAMACHANDRAN, K. K.; GENET, C.; MAR*, A.; J. Solid State Chem. 231 (2015) 204-211, http://dx.