  In iron pnictides, high temperature superconductivity emerges after
suppressing antiferromagnetism by doping. Here we show that antiferromagnetism
in Ca$_{1-x}$La$_x$FeAs$_2$ is robust against and even enhanced by doping.
Using $^{75}$As-nuclear magnetic resonance and nuclear quadrupole resonance
techniques, we find that an antiferromagnetic order occurs below the N\'eel
temperature $T_{\rm N}$ = 62 K at a high doping concentration ($x$ = 0.15)
where superconductivity sets in at the transition temperature $T_{\rm c}$ = 35
K. Unexpectedly, $T_{\rm N}$ is enhanced with increasing doping, rising up to
$T_{\rm N}$ = 70 K at $x$ = 0.24. The obtained phase diagram of this new system
enriches the physics of iron-based high-$T_{\rm c}$ superconductors.
