Rolling at right angles: Magnetic anisotropy enables dual-anisotropic active matter We report on an experimental active matter system with motion restricted to four cardinal directions. Our particles are magnetite-doped colloidal spheres driven by the Quincke electrorotational instability. The absence of a magnetic field (|𝑩|=0) leads to circular trajectories interspersed with short spontaneous runs. Intermediate fields (|𝑩|≲20mT) linearize the motion along the axis perpendicular to 𝑩. At high magnetic fields, we observe the surprising emergence of a second, distinct linearization along the axis parallel to 𝑩. With numerical simulations, we show that this behavior can be explained by anisotropic magnetic susceptibility. 112 6 American Physical Society application/pdf