Previously, it has been shown that in a spin-charge separated SU(2) Yang–Mills theory, (Euclidean) spacetime rotation invariance can be broken by an infinitesimal 1-cocycle that appears in the SO(4) boosts. Here we study in detail the structure of this 1-cocycle. In particular, we show that its non-triviality relates to the presence of a (Dirac) magnetic monopole bundle. We also compute the finite version of the cocycle.