Angular2 ngIf-else

i'am trying to load pictureA or pictureB. My first solution is like this:

 <img *ngIf="my_picture" src="" width="180" height="80" >
 <img *ngIf="default_picture && !my_picture" src="">

But i would like use if-else like on API-Reference:

<div *ngIf="condition; else elseBlock">...</div>
<ng-template #elseBlock>...</ng-template>

So i do it like this:

 <div *ngIf="my_picture; else elseBlock">
     <img src="" >
 </div>
 <ng-template #elseBlock>
      <img src="" >
 </ng-template>

But i get a big exception-stack:

zone.js:388 Unhandled Promise rejection: Template parse errors:
Can't bind to 'ngIfElse' since it isn't a known property of 'div'. ("
        -->

        <div [ERROR ->]*ngIf="my_picture; else elseBlock">
            <img src=""): UserComponent@15:13
Property binding ngIfElse not used by any directive on an embedded template. Make sure that the property name is spelled correctly and

all directives are listed in the "@NgModule.declarations". (" -->

        [ERROR ->]<div *ngIf="my_picture; else elseBlock">
            <img src="" width="180" height="8"): UserComponent@15:8
'ng-template' is not a known element

How can i reliaze simple if-else block?