A family of Einstein Randers metrics

Using Hawking Taub-NUT metric $g_a$ on $\mathbf{R}^4$, where $a$ is a positive real number and finding a 4-parameter family of Killing vector fields of $(\mathbf{R}^4,g_a)$, we construct a 5-parameter family of Einstein Randers metrics with non-constant flag curvature.