The technique of low-energy yield spectroscopy is applied to determine the valence band line-up at heterojunctions in which the overlayer does not cover the substrate. It is shown that by tuning the analysis energy, the contribution made by electrons that traverse the surface in the uncovered regions can be suppressed from the interface spectrum obtained from low-energy yield spectroscopy operating in the constant-final-state mode, thus allowing the determination of the band line-up without ambiguity. The method was applied to the c-Si/c-SiC heterostructure. A value of Delta E-V = 0.78 +/- 0.06 eV was found for the valence band discontinuity.111837613768