Although this group is Abelian, it has one-and two-dimensional real irreducible representations (irreps), which can give rise to Jahn-Teller effect for certain electronic configurations of the two-dimensional irrep . For example, the quintet anion (tpa)Fe -has doubly degenerate states at a C 3 structure. Unlike C 3v group, C 3 group does not have planes of symmetry, which would split a two-dimensional irrep into a symmetric and antisymmetric irrep with respect to the plane. Therefore, the two Jahn-Teller states would not fall into two different irreps, as it happens in a majority of symmetry-imposed degenerate states . The only Abelian subgroup of C 3 is C 1 , therefore the two degenerate states belong to the same irrep, giving rise to general conical intersection problem. As documented numerically and theoretically , the description of true conical intersections is problematic in EOM-CC due to the non-Hermitian nature of the theory. In our case this leads to issues with finding left vectors at the symmetric geometry. To overcome this problem, we run calculations at slightly asymmetric geometry, coming from DFT optimization (listed in SI). Although this geometry is asymmetric only at the magnitude of a symmetry threshold, it leads to a small artificial energy splitting (∼ 0.01 eV in the EOM-EA calculation from a neutral reference) of the states that should be degenerate. This artifact is small enough to be neglected in typical photochemical applications, but it affects the magnitude of spin-orbit splitting. To mitigate this issue, we average the energies of the states that should be degenerate by symmetry. it also splits the degenerate irreps (the symmetry of the system is no longer described by point group symmetry; it is now described by double group symmetry), and the lowest of them looks very similar to the structure shown in Fig. . We followed the state-interaction procedure in computation of the ZFS splittings: the arithmetically averaged SOC blocks were plugged in the matrix Hamiltonian and the unperturbed state energies were on the diagonal. Then the entire matrix was diagonalized to yield energy-split multiplet states.