Intra-unit-cell Magnetic Order in Stoichiometric La${}_2$CuO${}_4$

Muon spin rotation measurements supported by magnetization experiments have been carried out in a stoichiometric high-$T_c$ parent compound La${}_2$CuO${}_4$ in %the a temperature range from 2~K to 340~K and in transverse magnetic fields up to 5~T. Along with the antiferromagnetic local field, muon spin rotation spectra indicate presence of an additional source of magnetic field on the muon. The characteristic splitting of about 45~G coming from this additional magnetic field is consistent with spontaneous circulating currents model of Varma.