  We have studied EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$ by the measurements of
x-ray diffraction, electrical resistivity, thermopower, magnetic
susceptibility, magnetoresistance and specific heat. Partial substitution of As
with P results in the shrinkage of lattice, which generates chemical pressure
to the system. It is found that EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$ undergoes
a superconducting transition at 26 K, followed by ferromagnetic ordering of
Eu$^{2+}$ moments at 20 K. This finding is the first observation of
superconductivity stabilized by internal chemical pressure, and supplies a rare
example showing coexistence of superconductivity and ferromagnetism in the
ferro-arsenide family.
