[1][2] The first example of a tricritical point was shown by Robert B. Griffiths in a helium-3 helium-4 mixture.
[3] In condensed matter physics, dealing with the macroscopic physical properties of matter, a tricritical point is a point in the phase diagram of a system at which three-phase coexistence terminates.
It seems more convenient experimentally[6] to consider mixtures with four components for which one thermodynamic variable (usually the pressure or the volume) is kept fixed.
Historically, it was for a long time unclear whether a superconductor undergoes a first- or a second-order phase transition.
that distinguishes type-I and type-II superconductors (see also here) is large enough, vortex fluctuations become important which drive the transition to second order.
The prediction was confirmed in 2002 by Monte Carlo computer simulations.