This paper explores the topological properties of alternagnets, focusing on mirror Chern bands and Weyl nodal loops. Alternagnets are collinear magnetic configurations that do not exhibit macroscopic magnetization, characterized by time-reversal symmetry and crystalline symmetries. The electronic spectra of alternagnets exhibit unconventional Zeeman splitting between bands of opposite spins, which arises from the interplay of these symmetries. The paper demonstrates that even with small spin-orbit coupling (SOC), the direction of the magnetic moments significantly influences the electronic spectrum, enabling novel topological phenomena. In two-dimensional (2D) alternagnets, the absence of SOC leads to Dirac crossings between bands of the same spin but opposite sublattices, forming mirror Chern bands that enable the quantum spin Hall effect. When SOC is introduced, these Dirac crossings are gapped, resulting in a mirror Chern insulator. In three-dimensional (3D) alternagnets, the crossings persist even with SOC, forming Weyl nodal loops protected by mirror symmetry. The direction of the magnetic moments determines the fate of these crossings, with out-of-plane moments preventing the anomalous Hall effect. The paper investigates microscopic models for 2D and 3D alternagnets, motivated by materials like rutile. It shows that the direction of the magnetic moments affects the topological properties, with out-of-plane moments leading to mirror Chern bands and in-plane moments leading to Weyl nodal loops. The study highlights the importance of magnetic moment orientation in controlling the topological behavior of alternagnets, offering insights into potential applications in spintronics and superconducting heterostructures. The results demonstrate the rich topological landscape of alternagnets and their potential for novel electronic and magnetic phenomena.This paper explores the topological properties of alternagnets, focusing on mirror Chern bands and Weyl nodal loops. Alternagnets are collinear magnetic configurations that do not exhibit macroscopic magnetization, characterized by time-reversal symmetry and crystalline symmetries. The electronic spectra of alternagnets exhibit unconventional Zeeman splitting between bands of opposite spins, which arises from the interplay of these symmetries. The paper demonstrates that even with small spin-orbit coupling (SOC), the direction of the magnetic moments significantly influences the electronic spectrum, enabling novel topological phenomena. In two-dimensional (2D) alternagnets, the absence of SOC leads to Dirac crossings between bands of the same spin but opposite sublattices, forming mirror Chern bands that enable the quantum spin Hall effect. When SOC is introduced, these Dirac crossings are gapped, resulting in a mirror Chern insulator. In three-dimensional (3D) alternagnets, the crossings persist even with SOC, forming Weyl nodal loops protected by mirror symmetry. The direction of the magnetic moments determines the fate of these crossings, with out-of-plane moments preventing the anomalous Hall effect. The paper investigates microscopic models for 2D and 3D alternagnets, motivated by materials like rutile. It shows that the direction of the magnetic moments affects the topological properties, with out-of-plane moments leading to mirror Chern bands and in-plane moments leading to Weyl nodal loops. The study highlights the importance of magnetic moment orientation in controlling the topological behavior of alternagnets, offering insights into potential applications in spintronics and superconducting heterostructures. The results demonstrate the rich topological landscape of alternagnets and their potential for novel electronic and magnetic phenomena.