Superconducting gap anisotropy caused by a spin-density wave

The Bardeen-Cooper-Schrieffer gap equation for {Δ}(k) is solved analytically for a simple metal having a spiral or linear spin-density wave. {Δ} falls to zero at the spin-density-wave energy gap for the spiral case, but falls to a finite (but small) value if the spin-density wave is linearly polarized. The electronic heat capacity in the superconducting state acquires a low-temperature tail, far in excess of a BCS exponential falloff, and similar to the (hitherto enigmatic) behavior observed in pure Pb.