Quaternionic Electron Theory: Geometry, Algebra and Dirac's Spinors
  The use of complexified quaternions and $i$-complex geometry in formulating the Dirac equation allows us to give interesting geometric interpretations hidden in the conventional matrix-based approach. 
Stefano De Leo (Dip. di Fisica, INFN, Lecce, Italia), Waldyr A.   Rodrigues, Jr. (UNICAMP/IMECC, Campinas, Brasil)