We present measurements of the magnetic susceptibility χ and the magnetization M of single crystals of metallic Yb2Pt2Pb, 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 TN =2.02 K from a paramagnetic liquid of Ybdimers, having a gap ∆=4.6 K between the singlet ground state and the triplet excited states. Magnetic fields suppress the AF order, which vanishes at a 1.25 T quantum critical point. The spin gap ∆ 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 Yb2Pt2Pb 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.PACS numbers: 75.10. Kt,75.20.Hr,75.30.Kz Much interest has focused on systems with geometrical frustration, where conventional antiferromagnetic (AF) order is suppressed in favor of more exotic ground states. The Shastry Sutherland Lattice (SSL) is one of the simplest frustrated systems [1], consisting of planes of orthogonal dimers of moments with interdimer coupling J ′ and the intradimer coupling J. The T=0 phase diagram has two limiting behaviors, depending on J ′ /J. Nonordering dimers are found for small J ′ /J, distinguished by an energy gap ∆ between the singlet and triplet states of the dimer. Insulating SrCu 2 (BO 3 ) 2 exemplifies this disordered 'spin liquid'(SL) regime [2][3][4]. Conversely, AF order with gapless magnetic excitations is favored for large J ′ /J, and the RB 4 (R= Gd,Tb,Dy,Ho,Er) compounds may represent this limit [5][6][7][8]. A T=0 transition between the SL and AF phases has been predicted for J ′ /J ≃0.6 -0.7 [3, 9-11], although symmetry-based arguments [12]