ZrCuSiAs: A “filled” PbFCl type

ZrCuSiAs is tetragonal, space group $\text{P4}\text{nmm}\text{, a = 3.6736, c = 9.5712}$Å, Z = 2. The structure is a “filled” PbFCl type, or it may alternatively be regarded as a tetragonally distorted MnCu₂Al (Heusler) structure. HfCuSiAs is iso-structural. Bonding in PbFCl-related structures is discussed.