Synthesis. All manipulations of the starting materials as well as reaction products were done in an argon-filled glove-box with O2 and H2O level < 0.1 ppm. For the synthesis, stoichiometric mixtures of the elements (all from ABCR GmbH, Karlsruhe, Germany) Ba (rods, 99.3%), In (tears shape, 99.9%), Zn (blocks, 99.95+%) and, Bi (pieces, 99.999%+) were loaded in a niobium ampoule which were sealed on both ends by arc-melting and, in turn, enclosed in evacuated fused silica Schlenk tube to protect from air oxidation at high temperature. The compound Ba8Zn2-xIn3+xBi10 (experimental: 0.21 ≤ x ≤ 0.47) were obtained by heating the mixtures with the stoichiometries Ba5ZnnIn4-nBi5 (n = 1, 1.5, 2 and 3) at 750°C within 6 h, annealed for 24 hours and then slowly cooling down to room temperature at the rate of -6°C/h. The compositions were chosen to study the effects on partial alio-valent Zn for In substitution in the previously reported ternary phase Ba5In4Bi5. Only the reactions with n = 1, 1.5, and 2 produced the title compound in the polyphasic products. While n = 3 yields only the ternary phase Ba2ZnBi2. Best quality single crystals suitable for X-ray diffraction were obtained from the starting mixture with n = 1 also, resulting in the highest yield according to X-ray powder diffraction. Later attempts to prepare the compound from stoichiometric mixtures also failed, and it seems to form only with Ba excess in the starting mixture relative to the established stoichiometry according to single crystal X-ray diffraction data.