  Neutron diffraction measurements were carried out on single crystals and
powders of Yb2Pt2Pb, where Yb moments form planes of orthogonal dimers in the
frustrated Shastry-Sutherland Lattice (SSL). Yb2Pt2Pb orders
antiferromagnetically at TN=2.07 K, and the magnetic structure determined from
these measurements features the interleaving of two orthogonal sublattices into
a 5*5*1 magnetic supercell that is based on stripes with moments perpendicular
to the dimer bonds, which are along (110) and (-110). Magnetic fields applied
along (110) or (-110) suppress the antiferromagnetic peaks from an individual
sublattice, but leave the orthogonal sublattice unaffected, evidence for the
Ising character of the Yb moments in Yb2Pt2Pb. Specific heat, magnetic
susceptibility, and electrical resistivity measurements concur with neutron
elastic scattering results that the longitudinal critical fluctuations are
gapped with E about 0.07 meV.
