  We carry out an exploratory study of the isospin one a0(980) and the isospin
one-half kappa scalar mesons using Nf=2+1+1 Wilson twisted mass fermions at one
lattice spacing. The valence strange quark is included as an Osterwalder-Seiler
fermion with mass tuned so that the kaon mass matches the corresponding mass in
the unitary Nf=2+1+1 theory. We investigate the internal structure of these
mesons by using a basis of four-quark interpolating fields. We construct
diquark-diquark and molecular-typecinterpolating fields and analyse the
resulting correlation matrices keeping only connected contributions. For both
channels, the low-lying spectrum is found to be consistent with two-particle
scattering states. Therefore, our analysis shows no evidence for an additional
state that can be interpreted as either a tetraquark or a tightly-bound
molecular state.
