  It is known that a solution of the tetrahedron equation generates infinitely
many solutions of the Yang-Baxter equation via suitable reductions. In this
paper this scheme is applied to an oscillator solution of the tetrahedron
equation involving bosons and fermions by using special 3d boundary conditions.
The resulting solutions of the Yang-Baxter equation are identified with the
quantum R matrices for the spin representations of B^{(1)}_n, D^{(1)}_n and
D^{(2)}_{n+1}.
