  Studies of the copper-based superconductors demonstrate how their phase
diagram becomes more complex as experimental probes improve, able to
distinguish among subtly different electronic phases. One of those phases,
nematicity, has become the matter of great interest also in the iron-based
superconductors, where it is detected deep in the tetragonal state. Here we
present the evolution of the in-plane Nernst effect anisotropy in the strain
detwinned Ca(Fe1-xCox)2As2 single crystals, whose behaviour can be explained
within the approach developed to describe the nematic order parameter in liquid
crystals [1,2]. Furthermore, the employed method turns out to be universally
applicable to data from other superconductors: Ba(Fe1-xCox)2As2 [3] as well as
YBa2Cu3Oy [4]. We conclude the observed broken rotational symmetry of the
electronic system is a consequence of the emerging thermodynamic electronic
nematic order at a temperature much higher than onset of the magnetic and
structural transitions.
