  Since topological insulators were theoretically predicted and experimentally
observed in semiconductors with strong spin-orbit coupling, more and more
attention has been drawn to topological materials which host exotic surface
states. These surface excitations are stable against perturbations since they
are protected by global or spatial/lattice symmetries. Succeeded in achieving
various topological insulators, a tempting challenge now is to search for
metallic materials with novel topological properties. Here we predict that
orthorhombic perovskite iridates realize a new class of metals dubbed
topological crystalline metals, which support zero-energy surface states
protected by certain lattice symmetry. These surface states can be probed by
photoemission and tunnelling experiments. Furthermore, we show that by applying
magnetic fields, the topological crystalline metal can be driven into other
topological metallic phases, with different topological properties and surface
states.
