  This document contains information supplementary to the article [1], but it
is self-contained and can be read independently as a pedagogical review. In the
first part, we explain our conventions for the tight-binding description of
electronic states on the hexagonal Bravais lattice in two dimensions. We derive
the Rashba spin splitting from elementary symmetry conditions, and subsequently
construct a minimal tight-binding model which displays Rashba spin splitting
near the center of the Brillouin zone. Furthermore, we derive the corresponding
symmetry conditions for a two-particle interaction in a second-quantized
framework. In the second part, we describe our conventions for the temperature
Green functions, in terms of which the renormalization group equations in [1]
have been formulated. We also provide a brief summary of the most important
definitions and properties of temperature Green functions.
  [1] G. A. H. Schober, K.-U. Giering, M. M. Scherer, C. Honerkamp, and M.
Salmhofer, arXiv:1409.7087.
