angular material 2 - autocomplete does not work

Question

I’m having a problem, the Angular Material auto complete does not work in my code. Loading the page does not appear nor the options.

html

<div class="form-group col-md-6 form-md-line-input" style="margin-top:0px;">
    <input matInput formControlName="devedor" type="text" class="form-control" id="form_control_4" [matAutocomplete]="auto" (input)="getDevedor()">
    <!-- <i class="fa fa-spinner"></i> -->
    <mat-autocomplete #auto="matAutocomplete">
        <mat-option *ngFor="let option of filteredOptions | async" [value]="option">
            {{option}}
        </mat-option>
    </mat-autocomplete>
    <label for="form_control_4">Ente devedor</label>
</div>

typescript

export class FiltroComponent implements OnInit {

  options: string[] = ['One', 'Two', 'Three'];
  filteredOptions: Observable<string[]>;

ngOnInit() {
  // AutoComplete Devedor
  this.filteredOptions = this.rForm.get("devedor").valueChanges
    .pipe(
      startWith(''),
      map(value => this._filter(value))
    );
  // End Of AutoComplete Tribunal

}

private _filter(value: string): string[] {
  const filterValue = value.toLowerCase();

  return this.options.filter(option => option.toLowerCase().includes(filterValue));
 }

In my view is the same as the documentation of Angualr Material, I have no idea why it is not working