  The topological classification of matter has been extended to include
semimetallic phases characterized by the presence of topologically protected
band degeneracies. In Weyl semimetals, the foundational gapless topological
phase, chiral degeneracies are isolated near the Fermi level and give rise to
the Fermi-arc surface states. However, it is now recognized that chiral
degeneracies are ubiquitous in the band structures of systems with broken
spatial inversion ($\mathcal{P}$) or time-reversal ($\mathcal{T}$) symmetry.
This leads to a broadly defined notion of topological metals, which implies the
presence of disconnected Fermi surface sheets characterized by non-zero Chern
numbers inherited from the enclosed chiral degeneracies. Here, we address the
possibility of experimentally observing surface-related signatures of chiral
degeneracies in metals. As a representative system we choose bcc iron, a
well-studied archetypal ferromagnetic metal with two nontrivial electron
pockets. We find that the (110) surface presents arc-like resonances attached
to the topologically nontrivial electron pockets. These Fermi-arc resonances
are due to two different chiral degeneracies, a type-I elementary Weyl point
and a type-II composite (Chern numbers $\pm 2$) Weyl point, located at slightly
different energies close to the Fermi level. We further show that these surface
resonances can be controlled by changing the orientation of magnetization,
eventually being eliminated following a topological phase transition. Our study
thus shows that the intricate Fermi-arc features can be observed in materials
as simple as ferromagnetic iron, and are possibly very common in polar and
magnetic materials broadly speaking. Our study also provides methodological
guidelines to identifying Fermi-arc surface states and resonances, establishing
their topological origin and designing control protocols.
