Stabilizing the LaCoAl 4 Structure through Indium‐Magnesium Substitution in CeRhIn 4−x Mg x (x = 0.79 and 0.84) – An Indide with Magnesium Centered Indium Cubes

The intermetallic compounds CeRhIn 4−x Mg x (x = 0.79 and 0.84) were prepared from the elements in sealed tantalum ampoules in a high‐frequency furnace. The samples were investigated by X‐ray powder and single crystal diffraction: LaCoAl 4 type, Pmma , a = 829.5(2), b = 433.56(9), c = 740.2(2) pm, wR2 = 0.0458, 651 F 2 values, 25 variables for CeRhIn 3.21 Mg 0.79 and a = 831.44(10), b = 433.49(10), c = 741.04(10) pm, wR2 = 0.0543, 915 F 2 values, 25 variables for CeRhIn 3.16 Mg 0.84 . The indium atoms build up two‐dimensional networks perpendicular to the b axis in an AA stacking sequence leaving slightly distorted trigonal, square and pentagonal prismatic voids for the rhodium, magnesium, and cerium atoms. Both square prismatic voids show small magnesium/indium mixing. The shortest interatomic distances occur for the Rh–Mg contacts (257 pm). Together, the rhodium, indium, and magnesium atoms build up three‐dimensional [RhIn 4−x Mg x ] networks in which the cerium atoms fill distorted pentagonal channels.