Rare-earth intermetallics provide fertile ground for discovering complex magnetic states arising from the interplay of competing interactions and magnetic anisotropy. Here, the authors demonstrate remarkably diverse magnetism in Tb${}_2$IrAl${}_4$Ge${}_2$ and Er${}_2$IrAl${}_4$Ge${}_2$, the first Ir-based members of the Ln${}_2$MAl${}_4$Ge${}_2$ family. Despite sharing the same tetragonal structure, the two compounds display strikingly different H–T phase diagrams. The Tb compound orders antiferromagnetically at 25 K and undergoes field-induced metamagnetic transitions accompanied by pronounced magnetotransport signatures. Its Er counterpart exhibits three zero-field transitions and at least seven closely competing magnetic regions below 20 kOe. These findings establish Ir-based aluminogermanides as a promising platform for exploring field-induced phenomena and their coupling to electronic transport.

Two-dimensional systems in which electrons travel long distances without colliding (scattering) with defects are important for building quantum devices and circuits with interesting emergent physics. Such a system would be especially valuable if it were also superconducting and could be cleanly patterned into devices smaller than the average distance between electron scattering events. Combining all the above in a single material is difficult, and strontium titanate is one of the few material platforms where this could plausibly be achieved. In this work, the authors explored a promising approach to pattern and tune electron density on strontium titanate surfaces using hydrogen plasma and side gate voltages. They observed clean electron transport, with scattering lengths near 1-2 microns. But surprisingly, superconductivity was completely suppressed, even in the electron density range where it is typically robust in similar systems with stronger scattering. These results raise an important open question: why do clean electron transport and superconductivity in this material appear to be working against each other?