  Self-assembly of nanoparticles can enable composites with pre-designed
properties but remains challenged by reproducing structural diversity of atomic
and molecular crystals. We combine anisotropic elastic and weakly screened
electrostatic interactions to guide both orientational and triclinic positional
self-ordering of inorganic nanocrystals in a nematic fluid host. The lattice
periodicity of these low-symmetry colloidal crystals is more than an order of
magnitude larger than the nanoparticle size. Orientations of nanocrystals, as
well as crystallographic axes of ensuing triclinic colloidal crystals, are
coupled to the uniform alignment direction of the nematic host, which can be
readily controlled on large scales. We probe colloidal pair and many-body
interactions and demonstrate how triclinic crystals with orientational ordering
of the semiconductor nanorods emerge from competing long-range elastic and
electrostatic forces.
