  In a recent Letter, Fauque et al. [Phys. Rev. Lett. 96, 197001 (2006)]
reported the detection of a novel magnetic order in YBCO near the pseudogap
transition temperature T*. They remark that this magnetic order has not been
clearly identified by local probes and, in particular, by muon spin resonance.
The purpose of this Comment is to point out that this is untrue, and together
with the more recent detection of broken time reversal symmetry by polar Kerr
effect measurements [J. Xia et al. Phys. Rev. Lett. 100, 127002 (2008)], there
are now three very different kinds of experiments that provide evidence for
this magnetic transition.
