Relativistic multireference ab initio wave function calculations with the restricted active space second-order perturbation theory (RASPT2) were performed on thorocene and uranocene to determine the actinide N 4,5 -edge and carbon K-edge X-ray absorption near-edge structure (XANES) intensities andt he metal-ligand orbitalm ixingi nt he ground state and core-excited states. Calculated spectrali ntensities show very good agreement with the experiments and therefore allow detailed and unambiguous assignment of the observed spectral features. f-type covalent bonding or antibonding interactions are observed for thorocene in the core-excited states, thoughn ot in the ground state. This is because the molecular orbital of f symmetry,w hich is the in-phasec ombination of the ligand L f and the Th 5f f orbitals, can be populated with electrons in core-excited states, whereas it is essentially unoccupied in the ground state. For uranocene, the XANES spectra do not reveal much information beyondm ultipletb roadening, despite the presence of distinct peaks in the spectra. Every core-excited peak is best characterized by its own set of bond orbitals, as the excited state covalency is clearly different from the ground state covalency.[a] Dr.