  We propose an improved twist-averaging scheme for quantum Monte Carlo methods
that use converged Kohn-Sham or Hartree-Fock orbitals as the reference. This
twist-averaging technique is tailored to sample the Brillouin zone of magnetic
metals, although it naturally extends to nonmagnetic conducting systems. The
proposed scheme aims to reproduce the reference magnetization and achieves
charge neutrality by construction, thus avoiding the large energy fluctuations
and the postprocessing needed to correct the energies. It shows the most robust
convergence of total energy and magnetism to the thermodynamic limit when
compared to four other twist-averaging schemes. Diffusion Monte Carlo
applications are shown on nonmagnetic Al and ferromagnetic $\alpha$-Fe. The
cohesive energy of Al in the thermodynamic limit shows an excellent agreement
with the experimental result. Furthermore, the magnetic moments in $\alpha$-Fe
exhibit rapid convergence with an increasing number of twists.
