High‐Mobility Carriers in Germanene Derivatives

Abstract Buckled elemental analogs of graphene—2D‐Xenes silicene, germanene, and stanene—and their derivatives are predicted to host high‐mobility carriers. Experiments, however, have not as yet confirmed the predictions. Here, high‐mobility (exceeding 10⁴ cm² V⁻¹ s⁻¹) carriers are discovered in intercalated multilayer germanene. Epitaxial films of antiferromagnetic and diamagnetic MGe₂ are synthesized via topochemical reactions, followed by extensive studies of the atomic and magnetic structures. Quantum oscillations in MGe₂ resistance manifest quasi‐2D Fermi‐surface pockets with effective masses of carriers as low as 0.015 m_e, comparable to graphene. The detected signature of the chiral anomaly in magnetoresistance and nonzero Berry phases may indicate the topological nature of the MGe₂ electronic structure and charge transport. The discovery bridges the gap between theory and experiment, thus establishing 2D‐Xenes as promising building blocks in materials engineering. Concurrently, the combination of magnetism and high mobility in Eu‐intercalated germanene is attractive for spintronic applications.