  Motivated by the recent lattice QCD study of the $DD^*$ interaction at
unphysical quark masses, we perform a theoretical study of the $DD^*$
interaction in covariant chiral effective field theory (ChEFT). In particular,
we calculate the relevant leading-order two-pion exchange contributions. The
results compare favorably with the lattice QCD results, supporting the
conclusion that the intermediate-range $DD^*$ interaction is dominated by
two-pion exchanges and the one-pion exchange contribution is absent. At a
quantitative level, the covariant ChPT results agree better with the lattice
QCD results than their non-relativistic counterparts, showing the relevance of
relativistic corrections in the charm sector.
