Towards Unreasonable Effectiveness in Five Dimensions

We discuss four-derivative corrections to pure $\mathcal{N}=2$, $D=5$ gauged supergravity, up to field redefinitions. In particular, the possible four-derivative corrections can be parametrized on-shell by a basis of five terms. We have found that, up to factors of the two-derivative action, supersymmetry picks out a unique set of coefficients for these terms, ie, there is a unique five-dimensional superinvariant at the four-derivative level.