Angular 2：无法绑定到 x，因为它不是已知的本机属性

在角2分量中，我有authbox.component.ts

import {Component} from 'angular2/core';
import {COMMON_DIRECTIVES} from 'angular2/common';
import {Credentials} from './credentials'
@Component({
    selector: 'authbox',
    template: `<div>
       <div class="login-panel" *NgIf="!IsLogged">
            <input type="text" *NgModel="credentials.name" />
            <input type="password" *NgModel="credentials.password" />
            <button type="button" (click)="signIn(credentials)">→| Sign In</button>
        </div>
        <div class="logged-panel" *NgIf="IsLogged">
            <span>{nickname}</span>&nbsp;&nbsp; <button type="button" (click)="signOut()">|→ Sign out</button>
        </div>
    </div>`,
    directives: [COMMON_DIRECTIVES]
})


export class AuthBoxComponent {

    private _isLogged: boolean;

    get IsLogged(): boolean {
        return this._isLogged
    }
    set IsLogged(value: boolean) {
        this._isLogged = value;
    }

    public credentials: Credentials;

}

在浏览器中，我得到了错误«Can't bind to 'NgModel' since it isn't a known native property»和«Can't bind to 'NgIf' since it isn't a known native property».

我用的是beta 8.