High-Order Anisotropic Magnetoresistance in a Cubic Ferromagnet.

High-order anisotropic magnetoresistance (AMR) is observed up to the 18th harmonic in cubic Fe(001) thin films, overturning the long-standing paradigm that only two-fold and four-fold terms are symmetry-allowed. Using angle-resolved transport and Fourier analysis, we show that six-fold and higher-order terms are intrinsic, tunable by temperature and thickness, and predicted by crystal symmetry. Microscopically, the two-fold sign reversal arises from a crossover between weak and strong scattering regimes, while high-order terms emerge from the interplay of anisotropic Fermi velocity and relaxation time. Our results establish high-order AMR as a symmetry-prescribed property of cubic ferromagnets, providing critical benchmarks for spin-orbit transport theory and enabling new angular-sensitive spintronic functionalities.