  The structural properties of the CaFe2As2 have been investigated by x-ray and
neutron powder diffraction techniques as a function of temperature. Unambiguous
experimental evidence is shown for coexistence of tetragonal and orthorhombic
phases below 170 K in contrast to existing literature. Detailed Rietveld
analyses of thermo-diffractograms show that the sample does not transform
completely in to the orthorhombic phase at the lowest temperature even though
it is the majority phase. We have found that the unit cell volume of the
orthorhombic phase is higher compared to that of the tetragonal phase for all
the temperatures. X-ray data on CaFe2As2 shows anomalous (at) lattice parameter
contraction with increasing temperature and phase co-existence behavior below
170 K unlike other members of the 122 family of compounds like SrFe2As2 and
EuFe2As2. Temperature dependent magnetization of polycrystalline CaFe2As2
sample show weak anomalies below 170 K. This behavior of the polycrystalline
sample is in contrast to that of a single crystal reported earlier.
