High-order Dy multipole motifs observed in DyB2C2 with resonant soft   x-ray Bragg diffraction
  Resonant soft x-ray Bragg diffraction at the Dy M4,5 edges has been exploited to study Dy multipole motifs in DyB2C2. Our results are explained introducing the intra-atomic quadrupolar interaction between the core 3d and valence 4f shell. This allows us to determine for the first time higher order multipole moments of dysprosium $4f$ electrons and to draw their precise charge density. The Dy hexadecapole and hexacontatetrapole moment have been estimated at -20% and +30% of the quadrupolar moment, respectively. No evidence for the lock-in of the orbitals at T_N has been observed, in contrast to earlier suggestions. The multipolar interaction and the structural transition cooperate along c but they compete in the basal plane explaining the canted structure along [110]. 
A.M. Mulders, U. Staub, V. Scagnoli, S.W. Lovesey, E. Balcar, T.   Nakamura, A. Kikkawa, G. van der Laan and J.M. Tonnerre