Competing Ordering Modes in the Distorted Quantum Kagome Material Clinoatacamite Cu_{2}Cl(OH)_{3}

We have studied the magnetic properties of clinoatacamite Cu_{2}Cl(OH)_{3}, the parent compound of the quantum spin liquid candidate herbertsmithite and a long-standing puzzle among frustrated quantum magnets. As we reveal using density-functional theory, clinoatacamite belongs to the class of distorted kagome antiferromagnets with the kagome plane being embedded into a low-symmetry crystal structure. By means of thermodynamic measurements, muon spin rotation and relaxation, as well as neutron diffraction on single crystals, we find in zero magnetic field complex behavior below T_{I}=18.1  K which unfolds in three temperature regions I-III. We propose this complexity in multicritical clinoatacamite to arise from the competition of antiferromagnetic ordering modes from the underconstrained manifold of modes, which can lead to a metamagnetic texture in zero field.