The propagati on characteristics of low-fr equency (in compariso n wit h the electron cyclotron fre- quency) surface (LFS ) plasma waves propagating at the interface of a quantum plasma slab are studied in the presence of a unifo rm external magnet ic field. A quantum hydrodynam ic model is used, and the effects of the Ferm i pressure, the quantum force (as a gradient of the Bohm potential), as well as the Coulomb exchange interaction force, associated with the spin polarizatio n o f electrons, are considered to derive the dispersion relation for LFS waves. It is found that the dispersion properties of such LFS waves are sign ificantly modified by this new quantum effect. It is also shown tha t when the spin polarizati on effect is increased, the contribution of the Coulomb exchange potential becomes hig her than those of the Fermi-pressu re and the particle dispersion (Bohm potential). Furt hermore, the frequency of the surface wave is seen to be down-shi fted by the influence of the Coulomb exchange interaction force.
