Here you can find an all-electron basis set for group 14 elements:
C, Si, Ge Sn, and Pb. The contraction coefficients were
reoptimised with a relativistic method (RESC).
It is a modified WTBS basis set of roughly
cc-pvtz quality and it is given in GAMESS format. Check GAMESS manual for
details.
Briefly, exponents are followed by contraction coefficients.
Note that l-shells are s and p-shells expanded over the same set of
exponents with separate contraction coefficients, first s and then p
contraction coefficients are given in each row.
You must use internal uncontraction in the resolutions of the identity
($RELWFN uncon=1 $END) when using this basis set.
For all details and references check the following paper that you are
requested to quote if using this basis set:
W. Lie, D.G. Fedorov, K. Hirao, J. Phys. Chem. A, submitted for publication.
The basis can be taken from here.