We present measurements of the magnetic susceptibility χ and the magnetization M of single crystals of metallic , where localized Yb moments lie on the geometrically frustrated Shastry-Sutherland Lattice (SSL). Strong magnetic frustration is found in this quasi-two dimensional system, which orders antiferromagnetically (AF) at T_N=2.02 K from a paramagnetic liquid of Yb-dimers, having a gap Δ=4.6 K between the singlet ground state and the triplet excited states. Magnetic fields suppress the AF

more »

... rder, which vanishes at a 1.25 T quantum critical point. The spin gap Δ persists to 1.5 T, indicating that the AF degenerates into a liquid of dimer triplets at T=0. Quantized steps are observed in M(B) within the AF state, a signature of SSL systems. Our results show that is unique, both as a metallic SSL system that is close to an AF quantum critical point, and as a heavy fermion compound where geometrical frustration plays a decisive role.