  Geometrical frustration describes situations where interactions are
incompatible with the lattice geometry and stabilizes exotic phases such as
spin liquids. Whether geometrical frustration of magnetic interactions in
metals can induce unconventional quantum critical points is an active area of
research. We focus on the hexagonal heavy fermion metal CeRhSn where the Kondo
ions are located on distorted kagome planes stacked along the c axis.
Low-temperature specific heat, thermal expansion and magnetic Gr\"uneisen
parameter measurements prove a zero-field quantum critical point. The linear
thermal expansion, which measures the initial uniaxial pressure derivative of
the entropy, displays a striking anisotropy. Critical and noncritical behaviors
along and perpendicular to the kagome planes, respectively, prove that quantum
criticality is driven by geometrical frustration. We also discovered a
spin-flop-type metamagnetic crossover. This excludes an itinerant scenario and
suggests that quantum criticality is related to local moments in a spin-liquid
like state.
