emp-tree.component.html

 <mat-tree [dataSource]="dataSource" [treeControl]="treeControl">
   <mat-tree-node *matTreeNodeDef="let node" matTreeNodePadding>
     <button mat-icon-button disabled></button>
     {{node.item}}
   </mat-tree-node>
   <mat-tree-node *matTreeNodeDef="let node; when: hasChild" matTreeNodePadding>
     <button mat-icon-button
             [attr.aria-label]="'toggle ' + node.item" matTreeNodeToggle>
       <mat-icon class="mat-icon-rtl-mirror">
         {{treeControl.isExpanded(node) ? 'expand_more' : 'chevron_right'}}
       </mat-icon>
     </button>
     <a mat-button *ngIf="node.id !== 0" [routerLink]="['/', 'emp',node.id]">{{node.item}}</a>
     <span *ngIf="node.id === 0" >{{node.item}}</span>

     <app-sal-minimal  *ngIf="node.id !== 0" [empId]="node.id"></app-sal-minimal>

     <mat-progress-bar *ngIf="node.isLoading"
                       mode="indeterminate"
                       class="example-tree-progress-bar"></mat-progress-bar>
   </mat-tree-node>
 </mat-tree>