lpp3d1 = ListPointPlot3D[{#[[3 ;; 5]]} & /@ Sidata1,
PlotStyle -> colorsSi, AxesLabel -> {"q", "s2", "α"},
ImageSize -> Large,
LabelStyle -> {18}, PlotLabel -> Style["Si", 24]];24], ViewPoint -> {-3, -2, 1}];
###1.
Remove braces from {#[[3 ;; 5]]} &
in the first argument of ListPointPlot3D
and use replacement rule Point -> Line
:
ListPointPlot3D[#[[3 ;; 5]] & /@ Sidata1]Sidata1, PlotStyle -> colorsSi,
AxesLabel -> {"q", "s2", "\[Alpha]"}, ImageSize -> Large,
LabelStyle -> {18}, PlotLabel -> Style["Si", 24],
ViewPoint -> {-3, -2, 1}] /. Point -> Line
###2.
If you want the line retain colors associated with points, use a more elaborate replacement rule:
lpp3d1 /. points : {{Directive[_, _], Point[_]} ..} :>
{Thick, Line[points[[All, 2, 1, 1]], VertexColors -> points[[All, 1, 2]]]}
If you want to show both the points and the lines, use
lpp3d1 /. points : {{Directive[_, _], Point[_]} ..} :>
{points, Thick, Line[points[[All, 2, 1, 1]], VertexColors -> points[[All, 1, 2]]]}