  We consider the problem of symmetry decomposition of the entanglement
negativity in free fermionic systems. Rather than performing the standard
partial transpose, we use the partial time-reversal transformation which
naturally encodes the fermionic statistics. The negativity admits a resolution
in terms of the charge imbalance between the two subsystems. We introduce a
normalised version of the imbalance resolved negativity which has the advantage
to be an entanglement proxy for each symmetry sector, but may diverge in the
limit of pure states for some sectors. Our main focus is then the resolution of
the negativity for a free Dirac field at finite temperature and size. We
consider both bipartite and tripartite geometries and exploit conformal field
theory to derive universal results for the charge imbalance resolved
negativity. To this end, we use a geometrical construction in terms of an
Aharonov-Bohm-like flux inserted in the Riemann surface defining the
entanglement. We interestingly find that the entanglement negativity is always
equally distributed among the different imbalance sectors at leading order. Our
analytical findings are tested against exact numerical calculations for free
fermions on a lattice.
