Tuning superconductivity in Eu(Fe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mrow><mml:mn>0.81</mml:mn></mml:mrow></mml:msub></mml:math>Co<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mrow><mml:mn>0.19</mml:mn></mml:mrow></mml:msub></mml:math>)<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:math>As<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:math>with magnetic fields

We present results of ac-magnetic susceptibility, dc-magnetization, and magnetotransport measurements on a single crystal of a magnetic Eu(Fe${}_{0.81}$Co${}_{0.19}$)${}_{2}$As${}_{2}$ superconductor. The compound undergoes two phase transitions: into a canted antiferromagnetic state at ${T}_{N}=16.5$ K and a superconducting state at ${T}_{c}\ensuremath{\sim}5.15$ K in a zero field. Based on our experimental results, we conclude that ${T}_{c}$ can further be increased up to 6.5 K with magnetic fields applied parallel to the $ab$ plane of crystals. We argue that the tuning superconductivity may be actuated by suppressing the ferromagnetic component along the c axis of the Eu${}^{2+}$ moments, diminishing the orbital pair-breaking effect.