The concept of ordered half antiperovskites (HAP) derives A 2 M 3 X 2 structures formally from metal‐rich intermetallic antiperovskites AM 3 X such as MgNi 3 C. It was developed within the last decade in Regensburg accompanied by fascinating discoveries of other groups. It extends the idea known for oxide structures related to perovskite such as cuprate superconductors: therein, the 3D M‐O network is cut to 2D sheets, that is YBaCu 2 O 7‐d . By systematic formation of unoccupied sites 3D interlinked MO 6 octahedra in perovskites are cut to 2D substructures with CuO 4 and CuO 5 units. To the best of our knowledge, a similar scheme was not described for antiperovskites AM 3 X, where X and M sites of perovskites are exchanged. MgNi 3 C is taken subsequently as reference example. First reported by Hütter and Stadelmaier it became famous as noncuprate nonoxide superconductor. We show that MX 6 and XM 6 units in perovskites AMX 3 and APs AM 3 X can be cut to MX 3 and XM 3 units to form 2D structures. The situation compares to gray As and black P that are derived from a primitive α‐Po structure by cutting three of the six bonds. In both cases, interlinked 3D networks are cut to 2D structures. However, the ternary compounds introduce additional degrees of freedom by varying the electron count by composition that turns out important to design properties such as for example magnetism and thermoelectrics of superconductivity. Consequently, the HAP concept consists of a crystal structure part for compounds A 2 M 3 X 2  = AM 3/2 L 3/2 X with AP superstructures and an electronic structure part. In this review, we point out relations to antiperovskite AM 3 X crystal and electronic structures, the history of A 2 M 3 X 2 compounds, the HAP concept, important discoveries of HAP materials and novel investigations on synthesis, spintronics, thermoelectrics, superconductors, and topological properties. Advantages of the given conceptual view are pointed out for computer modeling, design, and prediction of structures and functions.

Pb2AsxP14–x was synthesized by reacting the pnicogens in a lead melt in sealed silica ampoules. A mixture of hydrogen peroxide and glacial acetic acid removed lead from the final product. Pb2AsxP14–x represents the first lead arsenide phosphide adopting a new structure type. Systematic substitution of phosphorus by arsenic leads to the formation of Pb2AsxP14–x with x ~ 3.7, a compound with a two-dimensional arrangement of polypnictide layers, coordinated by Pb2+ cations. Pb2AsxP14–x is structurally related to PbP7 where a three-dimensional polyphosphide network is realized instead. The structure of Pb2As3.7(1)P10.3(1) was determined from single crystal X-ray diffraction data: space group P212121 (no. 19), a = 10.060(1), b = 10.500(1), c = 13.711(2) Å, and V = 1448.3(4) Å3. The structure is discussed relative to PbP7 focusing on the differences in the polyanionic substructures of the two polypnictides.