The paper investigates the magnetic properties of monolayer RuF4, a two-dimensional (2D) material, using density functional theory (DFT) and symmetry analysis. The study reveals that RuF4 is a 2D d-wave altern magnet, characterized by zero net magnetization and spin-split electronic bands. Spin-orbit coupling (SOC) introduces a significant spin splitting of the electronic bands by approximately 100 meV, transforming RuF4 into a weak ferromagnet due to non-trivial spin-momentum locking. The net magnetic moment scales linearly with the SOC strength. The authors derive an effective spin Hamiltonian that captures the spin-splitting and spin-momentum locking of the electronic bands. They also disentangle the effects of alternmagnetism and SOC-induced spin splitting, highlighting the impact of SOC on the alternmagnetic properties. The findings underscore the importance of non-trivial spin-momentum locking and weak ferromagnetism in 2D altern magnets, which have potential applications in novel areas of material science research.The paper investigates the magnetic properties of monolayer RuF4, a two-dimensional (2D) material, using density functional theory (DFT) and symmetry analysis. The study reveals that RuF4 is a 2D d-wave altern magnet, characterized by zero net magnetization and spin-split electronic bands. Spin-orbit coupling (SOC) introduces a significant spin splitting of the electronic bands by approximately 100 meV, transforming RuF4 into a weak ferromagnet due to non-trivial spin-momentum locking. The net magnetic moment scales linearly with the SOC strength. The authors derive an effective spin Hamiltonian that captures the spin-splitting and spin-momentum locking of the electronic bands. They also disentangle the effects of alternmagnetism and SOC-induced spin splitting, highlighting the impact of SOC on the alternmagnetic properties. The findings underscore the importance of non-trivial spin-momentum locking and weak ferromagnetism in 2D altern magnets, which have potential applications in novel areas of material science research.