  We consider states with a charge- or spin-density wave order parameter which
is odd in frequency, so that the order parameter vanishes at zero frequency and
there is a conventional Fermi surface. Such states break translational symmetry
and, therefore, are not conventional Fermi liquids. In the odd-frequency
spin-density wave case, there are Goldstone bosons and the low-energy spectrum
is manifestly different from that of a Fermi liquid. We discuss a simple model
which gives rise to such ordered states. The frequency-dependence of the gap
leads to an unusual temperature dependence for various thermodynamic and
transport properties, notably the resistivity.
