  Among high T_c materials, the YBCO (YBa_2Cu_3O_{7-x}) compounds are special
since they have superconducting chains as well as planes. We show that a
discontinuity in the density of states as a function of magnetic field may
appear at a new energy scale, characteristic of the chain and distinct from
that set by the d wave gap. This is observable in experimental studies of the
thermodynamical properties of these systems, such as the specific heat.
