In a recent paper [J. Podolsky and H. Ovcharenko, Kerr black hole in a uniform magnetic field: An exact solution, Phys. Rev. Lett. 135, 181401 (2025)], a new class of exact spacetimes in Einstein’s gravity describing Kerr black holes immersed in an external uniform magnetic field was proposed. In this work, we study the kinematic effects of spinning test particles orbiting this type of black hole, offering a valid test for particle motion under an external uniform magnetic field. By employing the Mathisson-Papapetrou-Dixon equations, we explore the dynamics of precessing orbits and characteristic orbital types, including circular orbits and innermost stable circular orbits. Our analysis reveals that the external magnetic field can significantly alter the topological structure of the effective potential, modifying orbital stability and potentially eliminating stable circular configurations. Furthermore, we demonstrate that an augmented magnetic field necessitates an increased orbital angular momentum to uphold spinning particles within these prograde characteristic orbits at equivalent radii. Notably, in the near-extremal black hole regime, sufficiently strong magnetic fields completely suppress retrograde circular orbits. These findings uncover the profound impact of magnetic fields on the trajectories of spinning particles, providing valuable theoretical insights into celestial motion in magnetized spacetimes.

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• Classical black holes
• General relativity
• Quantum aspects of black holes