The propagation characteristics of low-frequency (in comparison with the electron cyclotron frequency) surface (LFS) plasma waves propagating at the interface of a quantum plasma slab are studied in the presence of a uniform external magnetic field. A quantum hydrodynamic model is used, and the effects of the Fermi pressure, the quantum force (as a gradient of the Bohm potential), as well as the Coulomb exchange interaction force, associated with the spin polarization of electrons, are considered to derive the dispersion relation for LFS waves. It is found that the dispersion properties of such LFS waves are significantly modified by this new quantum effect. It is also shown that when the spin polarization effect is increased, the contribution of the Coulomb exchange potential becomes higher than those of the Fermi-pressure and the particle dispersion (Bohm potential). Furthermore, the frequency of the surface wave is seen to be down-shifted by the influence of the Coulomb exchange interaction force.
