  We report the results of a search for spontaneous magnetism due to a time
reversal symmetry breaking phase in the superconducting state of (110)-oriented
YBCO films, expected near the surface in this geometry. Zero field and weak
transverse field measurements performed using the low-energy muon spin rotation
technique with muons implanted few nm inside optimally-doped YBCO-(110) films
show no appearance of spontaneous magnetic fields below the superconducting
temperature down to 2.9 K. Our results give an upper limit of ~0.02 mT for
putative spontaneous internal fields.
