merge two networks in R igraph ggnet2

Question

I need to join two network graphs in R, just overposing the second on the first.

I share with you more detalis: My first graph is a maximum spanning tree in this form:

g1 <- graph_from_adjacency_matrix(m4, mode = "upper", weighted = T, diag = F)
max_spann_tree2 <- mst(g1, weights = -E(g)$weight)

max_spann_tree2<-asNetwork(max_spann_tree2)
ggnet2(max_spann_tree2 ,size =  nlav1,size.cut = 4, edge.size = 1, edge.color = "grey", color = "he1", color.legend = "industry", palette = "Set3")

max_spann_tree2 has this structure:

 > max_spann_tree2
     Network attributes:
      vertices = 181 
      directed = FALSE 
      hyper = FALSE 
      loops = FALSE 
      multiple = FALSE 
      bipartite = FALSE 
      total edges= 180 
        missing edges= 0 
        non-missing edges= 180 

 Vertex attribute names: 
    he1 vertex.names

and I need to overpose this graph

net55<-asNetwork(net5)
ggnet2(net55 ,size =  nlav5,size.cut = 4, edge.size = 1, edge.color = "grey", color = "he5", color.legend = "industry", palette = "Set3")

net5 has the following structure:

> net5

IGRAPH 3893673 UNW- 87 250 -- 
+ attr: name (v/c), he (v/c), nlav (v/n), ateco (v/c), weight (e/n)
+ edges from 3893673 (vertex names):
 [1] A1013--A1621 A1039--A1051 A1039--A1089 A1041--A1051 A1041--A1061 A1041--A1071 A1041--A1073 A1041--A2312
 [9] A1041--A2369 A1041--A2370 A1041--A2512 A1041--A6910 A1041--A6920 A1041--A7112 A1051--A2512 A1051--A7420
+ ... omitted several edges

I tried with uniongraph without success. Any suggestions to merge this two plot? Can I merge directly the two ggnet2 plot? Or should I do something else? thanks in advance