[Flow] Login show Username

[Patric Eckhart]

I have created a actioncontroller to manage frontend user. the user can register and login.
Now I would show the username in my template. I have tried the following function but I does not work.

{username} in my fluid template

/**
	 * @return \TYPO3\Flow\Security\Account
	 * @param string $identifier
	 * @return void
	 */
	public function indexAction() {
		$user = $this->account->getAccountIdentifier();
		$account = $this->accountRepository->findByAccountIdentifierAndAuthenticationProviderName($user, "DefaultProvider");
		$this->view->assign('username', $account);
	}

Can you help me?