  The Universal One-Loop Effective Action (UOLEA) is a general expression for
the effective action obtained by evaluating in a model-independent way the
one-loop expansion of a functional path integral. It can be used to match UV
theories to their low-energy EFTs more efficiently by avoiding redundant steps
in the application of functional methods, simplifying the process of obtaining
Wilson coefficients of operators up to dimension six. In addition to loops
involving only heavy fields, matching may require the inclusion of loops
containing both heavy and light particles. Here we use the recently-developed
covariant diagram technique to extend the UOLEA to include heavy-light terms
which retain the same universal structure as the previously-derived heavy-only
terms. As an example of its application, we integrate out a heavy singlet
scalar with a linear coupling to a light doublet Higgs. The extension presented
here is a first step towards completing the UOLEA to incorporate all possible
structures encountered in a covariant derivative expansion of the one-loop path
integral.
