Metallic systems with geometrically frustrated magnetic lattices are of considerable interest due to the exotic ground states that emerge from competing interactions and structural constraints that suppress conventional magnetic order. Here we report the synthesis and magnetic phase diagram of a suitable candidate, ${\mathrm{TbAl}}_2{\mathrm{Ge}}_2$ in a single-crystalline form, where the Tb atoms form a triangular-net arrangement. Magnetization, heat capacity, and electrical resistivity measurements establish an antiferromagnetic ground state in the system with two transitions at $T_{N1}\approx$ 15 K and $T_{N2} \approx$ 11 K, while applied magnetic fields reveal a rich temperature-magnetic field $\left(T\text{−}H\right)$ phase diagram. Both $T_{N1}$ and $T_{N2}$ get suppressed monotonically with increasing $H$, but the magnetic easy plane $(H\perp c)$ has an additional magnetic phase intermediate between the two phases bounded by $T_{N1}$ and $T_{N2}$. The transition of the AFM spins to a spin polarized state at relatively low magnetic fields motivated us to evaluate ${\mathrm{TbAl}}_2{\mathrm{Ge}}_2$ for the magnetocaloric effect. We obtain moderate values of magnetoentropy, rotational magnetocaloric effect, and relative cooling power in this system.

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• Entropy
• Fermi surface
• Magnetic phase transitions
• Crystal growth
• Magnetization measurements