The low energy spin excitation spectrum of the breathing pyrochlore Ba 3 Yb 2 Zn 5 O 11 has been investigated with inelastic neutron scattering. Several nearly resolution limited modes with no observable dispersion are observed at 250 mK while, at elevated temperatures, transitions between excited levels become visible. To gain deeper insight, a theoretical model of isolated Yb 3+ tetrahedra parametrized by four anisotropic exchange constants is constructed. The model reproduces the inelastic neutron scattering data, specific heat, and magnetic susceptibility with high fidelity. The fitted exchange parameters reveal a Heisenberg antiferromagnet with a very large Dzyaloshinskii-Moriya interaction. Using this model, we predict the appearance of an unusual octupolar paramagnet at low temperatures and speculate on the development of inter-tetrahedron correlations.Frustrated or competing interactions have been repeatedly found to be at the root of many unusual phenomena in condensed matter physics [1][2][3][4][5]. By destabilizing conventional long-range order down to low temperature, frustration in magnetic systems can lead to many exotic phases; from unconventional multipolar [6,7] and valence bond solid orders [1,4] to disordered phases such as classical and quantum spin liquids [1,4]. Significant attention has been devoted to understanding geometric frustration where it is the connectivity of the lattice that hinders the formation of order. Recently, however, magnets frustrated not by geometry but by competing interactions have become prominent for the novel behaviors that they host. Such competing interactions might be additional isotropic exchange acting beyond nearest neighbors [8-10], biquadratic or other multipolar interactions [11]. One possibility attracting ever increasing interest is that competing strongly anisotropic interactions may stabilize a wide range of unusual phenomena.An exciting research direction in the latter context concerns itself with so-called "quantum spin ice" [12]. This quantum spin liquid can be stabilized by perturbing classical spin ice with additional anisotropic transverse exchange interactions that induce quantum fluctuations. Particularly interesting is the potential realization of such physics in the rare-earth pyrochlores R 2 M 2 O 7 [13][14][15], where R is a trivalent 4 f rare-earth ion, and M is a non-magnetic tetravalent transition metal ion, such as M=Ti, Sn or Zr. These materials can be described in terms of pseudo spin-1/2 degrees of freedom interacting via anisotropic exchanges [12,15], where the effective spin-1/2 maps the states of the crystal-electric field ground doublet of the rare-earth ion. These materials display a wealth of interesting phenomena, from the possibility of quantum [16][17][18] ion is part of a large and small tetrahedron in the breathing pyrochlore lattice.liquids [22,23]. In many of these compounds, the physics is very delicate, showing strong sample to sample variations [24] or sensitivity to very small amounts of disorder [25,26]. Consequen...