  Superconductors involving electrons with internal degrees of freedom beyond
spin can have internally anisotropic pairing states that are impossible in
single-band superconductors. As a case in point, in even-parity multiband
superconductors that break time-reversal symmetry, nodes of the superconducting
gap are generically inflated into two-dimensional Bogoliubov Fermi surfaces.
The detection and characterization of these quasiparticle Fermi surfaces
requires the understanding of their experimental consequences. In this paper,
we derive the low-energy density of states for a broad range of possible nodal
structures. Based on this, we calculate the low-temperature form of observables
that are commonly employed for the characterization of nodal superconductors,
i.e., the single-particle tunneling rate, the electronic specific heat and
Sommerfeld coefficient, the thermal conductivity, the magnetic penetration
depth, and the NMR spin-lattice relaxation rate, in the clean limit. We also
address the question whether the topological invariant of the Bogoliubov Fermi
surfaces is associated with topologically protected surface states, with
negative results. This work is meant to serve as a guide for experimental
searches for Bogoliubov Fermi surfaces in time-reversal-symmetry-breaking
superconductors.
