Tricritical wings in UGe$_2$: A microscopic interpretation

In the present work we analyze the second order transition line that connect the tricritical point and the quantum critical ending point on the temperature--magnetic-field plane in UGe$_2$. For the microscopic modeling we employ the Anderson lattice model recently shown to provide a fairly complete description of the full magnetic phase diagram of UGe$_2$ including all the criticalities. The shape of the so-called tricritical wings, i.e. surfaces of the first-order transitions, previously reported by us to quantitatively agree with the experimental data, is investigated here with respect to the change of the total filling and the Land\'e factor for $f$ electrons which can differ from the free electron value. The analysis of the total filling dependence demonstrates sensitivity of our prediction when the respective positions of the critical ending point at the metamagnetic transition and tricritical point are mismatched as compared to the experiment.