[Wien] How to generate the C19 structure (alpha-Sm)?

[Claudio Cazorla Silva]

Dear wien2k users,
I want to calculate some of the properties of Y in the C19 (alpha-Sm) 
phase, however,
I'm finding some problems in generating the structure file with the 
Structgen program.
The primitive vectors of this lattice coincide with the rhombohedral 
ones, making c =  9*((2/3)**1.2),
and the basis vectors are three: b1 = (0,0,0), b2 = (0,0,2/9) and b3 = 
(0,0,-2/9), in cartesian coordinates.
The group symmetry corresponding to this structure is 166 R3_m.
I choose three inequivalent atoms, for the basis vectors, and option "R" 
in the StructGen interface, however,
when latter I initialize the calculations the correct group symmetry is 
not recognized and the C2/m is proposed instead.
Could any of you help with this? Many thanks in advance.

Dr. C. Cazorla Silva