Abstract: Coherence factors are a hallmark of superconductivity as a pair-condensation phenomenon. When electrons pair, quasi-particles develop an acute phase sensitivity to different types of scattering potential, described by the appearance of coherence factors in the scattering amplitudes. While the effects of phase-sensitive coherence factors are well established in isotropic superconductors, they are much harder to detect in their anisotropic counterparts, such as high-Tc cuprates, iron-based superconductors, or heavy-fermion superconductors. One of the recently developed technique to determine the phase structure of the superconducting order parameter is scanning tunneling microscopy (STM) which determines the dispersion of quasiparticle states from the quasiparticle interference (QPI) patterns induced by impurity scattering. Such experiments, performed in an external magnetic field, offer the capability of probing the phase of the superconducting order parameter by detecting a field enhancement of the sign preserving scattering that results from the sensitivity of QPI to the coherence factors associated with impurity scattering. In my talk I will review the experimental and theoretical results for layered cuprates and present calculations of the QPI patterns in iron-based superconductors and heavy fermion superconductor, CeCoIn5 where the symmetries of the superconducting gaps are still actively debated.