In-plane resistivity anisotropy in mechanically and magnetic field detwinned single crystals of EuFe$_{2}$As$_{2}$*

The in-plane resistivity of EuFe$_{2}$As$_{2}$ (Eu122) shows anomalies at the nematic/magnetic ordering temperature of Fe ions, $T_N^{Fe} \approx$ 190 K, as well as of Eu ions, $T_N^{Eu} \approx$ 19 K. When the crystal is detwinned by mechanical strain, resistivity along the $a-$ orthorhombic direction is lowered at all temperatures $T < T_N^{Fe}$, similar to other parent 122 compounds such as Sr122 and Ba122 [1]. Application of a 3 T in-plane magnetic field below $T_N^{Eu}$ leads to the structural detwinning with $a-$ axis following field direction and persistent up to $T_N^{Fe}$ [2]. On contrary, $a-$ axis direction is fixed in strained samples. \newline\newline [1]E. C. Blomberg et al., Phys. Rev. B 83, 134505 (2011) \newline [2]S. Zapf et al., Phys. Rev. Lett. 113, 227001 (2014) \newline [3]Y. Xiao et al., Phys. Rev. B 81, 220406 (2010)