Asymmetric Berry-Phase Interference Patterns in a Single-Molecule Magnet
  A Mn4 single-molecule magnet displays asymmetric Berry-phase interference patterns in the transverse-field (HT) dependence of the magnetization tunneling probability when a longitudinal field (HL) is present, contrary to symmetric patterns observed for HL=0. Reversal of HL results in a reflection of the transverse-field asymmetry about HT=0, as expected on the basis of the time-reversal invariance of the spin-orbit Hamiltonian which is responsible for the tunneling oscillations. A fascinating motion of Berry-phase minima within the transverse-field magnitude-direction phase space results from a competition between noncollinear magnetoanisotropy tensors at the two distinct Mn sites. 
H. M. Quddusi, J. Liu, S. Singh, K. J. Heroux, E. del Barco, S. Hill,   and D. N. Hendrickson
cond-mat.mes-hall