The two-dimensional magnetic triangular lattice, with rare-earth local moments coupled through long-range interactions and hosting strong spin-orbit coupling, serves as an ideal platform for exploring novel quantum phenomena. Here, we report the physical properties of ${\mathrm{DyNiAl}}_4{\mathrm{Ge}}_2$ single crystals through comprehensive structural, magnetic, heat capacity, electrical transport, and neutron powder diffraction measurements. ${\mathrm{DyNiAl}}_4{\mathrm{Ge}}_2$ crystallizes in a trigonal lattice with the space group $R\overline{3}m$, where Dy atoms form two-dimensional triangular lattice layers within the $\mathit{ab}$ plane and stack along the $c$ axis. Magnetic susceptibility measurement reveals a magnetic phase transition at $T_N$ = 9.0 K, further confirmed by the $\lambda$-shaped peak in the heat capacity curve. The obtained temperature-magnetic field phase diagram is relatively simple compared to other isostructural compounds, suggesting the absence of magnetic frustration. This is further evidenced by neutron powder diffraction, which shows a collinear antiferromagnetic ground state with a propagation vector $\mathit{k}$ = (0, 0, 1.5), implying the absence of magnetic frustration in ${\mathrm{DyNiAl}}_4{\mathrm{Ge}}_2$. In this magnetic structure, Dy moments are aligned ferromagnetically within each triangular layer and arranged antiferromagnetically between adjacent layers along the $c$ axis. Our results establish ${\mathrm{DyNiAl}}_4{\mathrm{Ge}}_2$ as a model system for understanding the interplay between RKKY interaction and geometrical frustration in this family of compounds.

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• Magnetic order
• Magnetic phase transitions
• Magnetism
• Rare-earth magnetic materials
• Magnetization measurements
• Neutron diffraction
• X-ray diffraction