We report the synthesis and comprehensive investigation of single-crystalline ${\mathrm{Tb}}_2{\mathrm{IrAl}}_4{\mathrm{Ge}}_2$ and ${\mathrm{Er}}_2{\mathrm{IrAl}}_4{\mathrm{Ge}}_2$, the first Ir-based members of the $L{n}_{2}M{\mathrm{Al}}_4{\mathrm{Ge}}_2$ family. Both compounds crystallize in the tetragonal ${\mathrm{Tb}}_2{\mathrm{NiAl}}_4{\mathrm{Ge}}_2$-type structure (space group $I4/mmm$) and exhibit easy-axis magnetic anisotropy with the crystallographic $c$ axis as the preferred magnetization direction. ${\mathrm{Tb}}_2{\mathrm{IrAl}}_4{\mathrm{Ge}}_2$ undergoes antiferromagnetic ordering below $T_N=25\mathrm{K}$ and develops a sequence of field-induced metamagnetic transitions accompanied by pronounced magnetotransport anomalies, including a nonlinear Hall response. In contrast, ${\mathrm{Er}}_2{\mathrm{IrAl}}_4{\mathrm{Ge}}_2$ exhibits three successive zero-field magnetic transitions and a substantially richer low-temperature magnetic phase diagram comprising multiple competing field-induced phases confined to relatively modest magnetic fields. The differences between the Tb- and Er-based compounds demonstrate the wide range of magnetic behavior that can be realized within the ${\mathrm{Tb}}_2{\mathrm{NiAl}}_4{\mathrm{Ge}}_2$-type structure. More broadly, the successful realization of Ir-based $L{n}_{2}M{\mathrm{Al}}_4{\mathrm{Ge}}_2$ compounds considerably expands the accessible chemical space of this family and opens a route to the exploration of related $4d$- and $5d$-based aluminogermanides.

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• Magnetic order
• Magnetism