We report the crystal structures and superconductivity (SC) of LaPt$_{ x}$Si$_{ 2-x}$ ($0.5 \leq x \leq 1.0$) that are solid solutions of LaSi$_{ 2}$ and LaPtSi with centrosymmetric tetragonal ($I4_{ 1}/amd$, $D_{ 4h}^{ 19}$, \#141) and non-centrosymmetric tetragonal ($I4_{ 1}md$, $C_{ 4v}^{ 11}$, \#109) structures, respectively. It was found that at $0.86 \leq x \leq 1.00$, the non-centrosymmetric tetragonal symmetry is preserved, while partial disorder appears in alternating Pt and Si of the hyper-honeycomb network. The superconducting transition temperature $T_{ \rm c}$ was drastically reduced from 3.9 K to 1.5 K as $x$ varies from 1.0 to 0.86. Additionally, a hexagonal phase with an AlB$_{ 2}$-type structure ($P6/mmm$, $D_{ 6h}^{ 1}$, \#191) has been discovered at $0.50 \leq x \leq 0.71$ with a honeycomb network of statistically distributed Pt and Si atoms. The hexagonal phase exhibited SC at $T_{ \rm c} = 0.38$ K. This system provides an opportunity to investigate the relationship between topological electronic states, SC, and disorders
Categories: cond-mat.supr-con cond-mat.str-el