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Electrical and thermal transport measurements on quenched NaCl-type Ag_1/3Pb_1/3Sb_1/3Se reveal an n-type semiconductor with a Seebeck coefficient up to −140 μVK⁻¹ and a thermal conductivity as low as 0.52 WmK⁻¹. Short-range order is indicated by disorder diffuse scattering in electron diffraction patterns. In contrast, ⁴<i>L</i>-Ag_0.61Pb_1.79Sb_2.61Se₆ (space group <i>Cmcm</i> with <i>a</i> = 4.2129(1) <i>Å</i>, <i>b</i> = 13.852(1) <i>Å</i>, and <i>c</i> = 20.866(1) <i>Å</i>, <i>Z</i> = 4) features the first lillianite-type structure in the system Ag/Pb/Sb/Se. It consists of slab-like NaCl-type building blocks that are interconnected via trigonal [PbSe₆] prisms. As such structures typically do not form with Te as an anion, the first “sulfosalt-like” compound, Ag_0.38Pb_0.25Sb_2.38Te₄, in the system Ag/Pb/Sb/Te forms a layered tetradymite-like structure (space group <i>R</i><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mover><mn>3</mn><mo>-</mo></mover></mrow></semantics></math></inline-formula><i>m</i> with <i>a</i> = 4.2887(1) <i>Å</i>, <i>c</i> = 41.544(1) <i>Å</i>, <i>Z</i> = 3). Its slabs, which are separated by van der Waals gaps, are built up from three layers of distorted [<i>M</i>Te₆] octahedra. Crystals of Ag_0.38Pb_0.25Sb_2.38Te₄ were grown by chemical transport.