  Symmetry breaking is a fundamental concept in condensed matter physics whose
presence often heralds new phases of matter. For instance, the breaking of time
reversal symmetry is traditionally linked to magnetic phases in a material,
while the breaking of gauge symmetry can lead to
superfluidity/superconductivity. Nematic phases are phases in which rotational
symmetry is broken while maintaining translational symme- try, and are
traditionally associated with liquid crystals. Electronic nematic states where
the or- thogonal in-plane crystal directions have different electronic
properties have garnered a great deal of attention after their discovery in
Sr$_3$Ru$_2$O$_7$, multiple iron based superconductors, and in the
superconducting state of CuBiSe. Here we demonstrate the existence of an
electronic ne- matic phase in the two-dimensional carrier gas that forms at the
(111) LaAlO$_3$ (LAO)/SrTiO$_3$ (STO) interface that onsets at low
temperatures, and is tunable by an electric field.
