Static density and concentration correlations in momentum space are determined quantitatively in molecular dynamics computer experiments on the interface between two liquid phases of a binary mixture. The interaction between spherical particles of equal sizes is modeled by 6-12 Lennard-Jones potentials. The resulting four density-density correlations are inverted to four direct correlation functions. Transformation to density-concentration variables inspired by the Bhatia-Thornton transformation and the hitherto unknown characteristic shapes of their projections, including the generalization of the Yvon-Zwanzig-Triezenberg projection, are discussed in detail; it is demonstrated that the q(4) coefficient again is negative. This precludes its interpretation as a rigidity coefficient. The interfacial contributions decay rather quickly with the momentum q, becoming totally submerged by short-range bulk and bulklike fluctuations at q-values of the order of 1/5 of the q-value of the nearest-neighbor (first) peak in the scattering factor.