The electron spin g- and hyperfine tensors of the endohedral metallofullerene Sc@C82 are anisotropic. Using electron spin resonance (ESR) and density functional theory (DFT), we can relate their principal axes to the coordinate frame of the molecule, finding that the g-tensor is not axially symmetric. The Sc bond with the cage is partly covalent and partly ionic. Most of the electron spin density is distributed around the carbon cage, but 5% is associated with the scandium d_yz orbital, and this drives the observed anisotropy.
@article{arxiv.0809.2029,
title = {Hyperfine structure of Sc@C82 from ESR and DFT},
author = {G. W. Morley and B. J. Herbert and S. M. Lee and K. Porfyrakis and T. J. S. Dennis and D. Nguyen-Manh and R. Scipioni and J. van Tol and A. P. Horsfield and A. Ardavan and D. G. Pettifor and J. C. Green and G. A. D. Briggs},
journal= {arXiv preprint arXiv:0809.2029},
year = {2010}
}