  We discuss in detail the constraints on partial compositeness coming from
flavour and CP violation in the leptonic sector. In a first part we present a
formulation of partial compositeness in terms of a flavour symmetry group and a
set of spurions, whose background values specify the symmetry breaking pattern.
In such a framework we construct the complete set of dimension-six operators
describing lepton flavour violation and CP violation. By exploiting the
existing bounds, we derive limits on the compositeness scale in different
scenarios, characterised by increasing restrictions on the spurion properties.
We confirm that in the most general case the compositeness scale should lie
well-above 10 TeV. However, if in the composite sector mass parameters and
Yukawa couplings are universal, such a bound can be significantly lowered,
without necessarily reproducing the case of minimal flavour violation. The most
sensitive processes are decays of charged leptons either of radiative type or
into three charged leptons, muon to electron conversion in nuclei and the
electric dipole moment of the electron. In a second part we explicitly compute
the Wilson coefficients of the relevant dimension-six operators in the
so-called two-site model, embodying the symmetry breaking pattern discussed in
our first part, and we compare the results with those of the general spurion
analysis.
