  We report the magnetism and transport measurements of CaCo$_2$As$_2$ and
Ca$_{0.9}$Sr$_{0.1}$Co$_2$As$_2$ single crystals. Antiferromagnetic transition
was observed at about 70 K and 90 K for CaCo$_2$As$_2$ and
Ca$_{0.9}$Sr$_{0.1}$Co$_2$As$_2$, respectively. Magnetism and magnetoresistance
measurements reveal metamagnetic transition from an antiferromagnetic state to
a ferromagnetic state with the critical field of 3.5 T and 1.5 T respectively
along c-axis for these two materials at low temperature. For the field along
ab-plane, spins can also be fully polarized above the field of 4.5 T for
Ca$_{0.9}$Sr$_{0.1}$Co$_2$As$_2$. While for CaCo$_2$As$_2$, spins can not be
fully polarized up to 7 T. We proposed the cobalt moments of these two
materials should be ordered ferromagnetically within the ab-plane but
antiferromagnetically along the c-axis(A-type AFM).
