  The three first sections contain an updated, not-so-short account of a partly
original approach to spinor geometry and field theories introduced by Jadczyk
and myself; it is based on an intrisic treatment of 2-spinor geometry in which
the needed background structures do not need to be assumed, but rather arise
naturally from a unique geometric datum: a vector bundle with complex
2-dimensional fibres over a real 4-dimensional manifold. The two following
sections deal with Dirac algebra and 4-spinor groups in terms of two spinors,
showing various aspects of spinor geometry from a different perspective. The
last section examines particle momenta in 2-spinor terms and the bundle
structure of 4-spinor space over momentum space.
