The ability of I···I van der Waals interactions to direct the self-assembly of slabs of the radical cation of ethylenedithio-1,2-diiodo-tetrathiafulvalene, EDT-TTF-I₂, and polymeric lead iodide covalent anionic layers is demonstrated by the synthesis of single crystals of β-(EDT-TTF-I₂)₂^•+[(Pb_5/6□_1/6I₂)^1/3-]₃, triclinic, P-1, a = 7.7818(8), b = 7.9760(8), c = 19.9668(2) Å, α = 82.409(12), β = 85.964(12), γ = 61.621(11)°, V = 1080.76(19) ų, R1, wR2 = 0.0459, 0.0947; and β-(EDT-TTF-I₂)₂^•+[(Pb_2/3+xAg_1/3-2x□_x I₂)^1/3-]₃, x ≈ 0.05, triclinic, P-1, a = 7.7744(8), b = 7.9193(8), c = 19.834(2) Å, α = 87.189(12), β = 83.534(12), γ = 61.602(11)°, V = 1067.4(2) ų, R1, wR2 = 0.0508, 0.0997. The state-of-the-art, combined microprobe and structural analysis of the metal site vacancies and occupancies patterns reveal a commensurate organic−inorganic interface and point out the importance of halogen···halogen van der Waals interactions to future studies aiming at directing interface topologies. The electronic structure, room-temperature metallic character and metal−insulator transition at ca. 70 K of the two-dimensional organic slabs are retained upon alloying of the inorganic sublattice with monocations. The room-temperature conductivity of the metallic lead−silver alloy is 2 orders of magnitude larger than that of β-(EDT-TTF-I₂)₂^•+[(Pb_5/6□_1/6I₂)^1/3-]₃. This calls for the study of materials with diverse alloying patterns with metal cations of different nature and charge.