Exceptional Coset Spaces and Unification in Six Dimensions
  The coset spaces E$_8$/SO(10)$\times$H$_F$ allow complex structures which can account for three quark-lepton generations including right-handed neutrinos. We show that in the context of supersymmetric SO(10) gauge theories in 6 dimensions they also provide the Higgs fields which are needed to break the electroweak and ${B-L}$ gauge symmetries, and to generate small neutrino masses via the seesaw mechanism. 
T. Asaka, W. Buchm\"uller, L. Covi