The aim of this proposal, which is part of a PhD project, is to investigate ordering of In and Sn in the solid solution Co3Sn2-xInxS2 (0<=x<=2). All members of this family of materials adopt the shandite structure, in which there are two crystallographically distinct main-group metal sites. Whilst the two end members are metallic, the electron transport properties of materials with intermediate compositions (0.75 <= x <= 1.5), which are semiconducting, are markedly different to those of the end members. In addition, the unit cell volume reaches a minimum value for x = 1. Ordering of In and Sn over the two available crystallographic sites, which exhibit very different coordination environments, could explain the anomalous dependence of the structure and properties of these materials with composition.