Unable to pre-select the radio button in the form by default

Ionic Framework ionic-v3
1

Ionic 4:

I have the the following form with radio buttons:

 <form [formGroup]="FormName" (ngSubmit)=sendData()>
    <ion-list>
      <ion-list-header>
        <ion-label>One</ion-label>
      </ion-list-header>
      <ion-radio-group [formControlName]="'products'">

        <ion-item>
          <ion-label>{{value1}}</ion-label>
          <ion-radio slot="start" value={{value1}} checked></ion-radio>
        </ion-item>

   <ion-item>
          <ion-label>{{value2}}</ion-label>
          <ion-radio slot="start" value={{value2}}'></ion-radio>
        </ion-item>

     </ion-radio-group>
    </ion-list>
</form>

I tried [checked] = “true”, [checked]=‘true,’ nothing works. How can I pre-select a radio button by default?

2 
checked = true ??
3

Still it does not work