The emergence of altermagnetism, a collinear magnetic phase characterized by momentum-dependent spin-split bands but zero net magnetization, has fundamentally reshaped the classification of magnetic order. We propose an altermagnetic (AM) order in a repulsive Hubbard model on the Lieb-5 lattice. Considering only nearest-neighbor hoppings within the lattice, we show a phase transition from the nonmagnetic phase to a unique AM isolated band metal phase (AMIM), allowing clear identification of spin-split states. Additionally, the AM metallic phase (AMM) is also shown to appear as an intermediate phase during the transition from the normal metal to the AMIM in the presence of diagonal hopping within each unit cell of the Lieb-5 lattice. The manifestation of distinct AM phases and the phase transitions, driven by the Hubbard interaction and hopping integrals, has been explored in terms of the spin-resolved band structure, spectral function, and behavior of the AM order parameter. The stability of these AM phases against the spin–orbit coupling and temperature is also established.

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• Altermagnetism
• Electronic structure
• Magnetic order
• Spin-orbit coupling
• 2-dimensional systems
• Hartree-Fock methods
• Hubbard model