  X-ray and Neutron diffraction as well as muon spin relaxation and M\"ossbauer
experiments performed on SrFe$_2$As$_2$ polycrystalls confirm a sharp first
order transition at $T_0 = 205$,K corresponding to an orthorhombic phase
distortion and to a columnar antiferromagnetic Fe ordering with a propagation
vector (1,0,1), and a larger distortion and larger size of the ordered moment
than reported for BaFe$_2$As$_2$. The structural and the magnetic order
parameters present an remarkable similarity in their temperature dependence
from $T_0$ down to low temperatures, showing that both phenomena are intimately
connected. Accordingly, the size of the ordered Fe moments scale with the
lattice distortion when going from SrFe$_2$As$_2$ to BaFe$_2$As$_2$.
Full-potential band structure calculations confirm that the columnar magnetic
order and the orthorhombic lattice distortion are intrinsically tied to each
other.
