  In this paper we explore the time-reversal-odd triple-correlation coefficient
in neutron beta decay, the so-called "D coefficient", using heavy-baryon
effective field theory with photon degrees of freedom. We find that this
framework allows us to reproduce the known results for the contribution which
comes from final-state interactions, and also to discuss higher-order
corrections. In particular we are able to show that in the heavy-baryon limit
all electromagnetic contributions vanish. By calculating the leading correction
to the known result, we give a final expression which is accurate to better
than 1%. Hence we extend downwards the range over which the D coefficient could
be used to explore time-violation from new physics.
